content/browser/devtools/protocol/tracing_handler.cc

// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "content/browser/devtools/protocol/tracing_handler.h"

#include <algorithm>
#include <cmath>
#include <memory>
#include <set>
#include <string>
#include <utility>
#include <vector>

#include "base/bind.h"
#include "base/format_macros.h"
#include "base/json/json_writer.h"
#include "base/memory/ref_counted_memory.h"
#include "base/optional.h"
#include "base/strings/strcat.h"
#include "base/strings/string_split.h"
#include "base/strings/stringprintf.h"
#include "base/time/time.h"
#include "base/timer/timer.h"
#include "base/trace_event/memory_dump_manager.h"
#include "base/trace_event/trace_event_impl.h"
#include "base/trace_event/tracing_agent.h"
#include "build/build_config.h"
#include "components/tracing/common/trace_startup_config.h"
#include "content/browser/devtools/devtools_agent_host_impl.h"
#include "content/browser/devtools/devtools_io_context.h"
#include "content/browser/devtools/devtools_stream_file.h"
#include "content/browser/devtools/devtools_traceable_screenshot.h"
#include "content/browser/devtools/devtools_video_consumer.h"
#include "content/browser/gpu/gpu_process_host.h"
#include "content/browser/renderer_host/frame_tree.h"
#include "content/browser/renderer_host/frame_tree_node.h"
#include "content/browser/renderer_host/navigation_request.h"
#include "content/browser/renderer_host/render_frame_host_impl.h"
#include "content/browser/renderer_host/render_widget_host_impl.h"
#include "content/browser/tracing/tracing_controller_impl.h"
#include "content/public/browser/browser_task_traits.h"
#include "content/public/browser/browser_thread.h"
#include "content/public/browser/tracing_service.h"
#include "mojo/public/cpp/bindings/receiver.h"
#include "mojo/public/cpp/bindings/remote.h"
#include "services/resource_coordinator/public/cpp/memory_instrumentation/memory_instrumentation.h"
#include "services/tracing/public/cpp/perfetto/perfetto_config.h"
#include "services/tracing/public/cpp/tracing_features.h"
#include "services/tracing/public/mojom/constants.mojom.h"
#include "services/tracing/public/mojom/perfetto_service.mojom.h"
#include "third_party/inspector_protocol/crdtp/json.h"

#ifdef OS_ANDROID
#include "content/browser/renderer_host/compositor_impl_android.h"
#endif

namespace content {
namespace protocol {

namespace {

const double kMinimumReportingInterval = 250.0;

const char kRecordModeParam[] = "record_mode";

// Frames need to be at least 1x1, otherwise nothing would be captured.
constexpr gfx::Size kMinFrameSize = gfx::Size(1, 1);

// Frames do not need to be greater than 500x500 for tracing.
constexpr gfx::Size kMaxFrameSize = gfx::Size(500, 500);

// Convert from camel case to separator + lowercase.
std::string ConvertFromCamelCase(const std::string& in_str, char separator) {
  std::string out_str;
  out_str.reserve(in_str.size());
  for (const char& c : in_str) {
    if (isupper(c)) {
      out_str.push_back(separator);
      out_str.push_back(tolower(c));
    } else {
      out_str.push_back(c);
    }
  }
  return out_str;
}

std::unique_ptr<base::Value> ConvertDictKeyStyle(const base::Value& value) {
  const base::DictionaryValue* dict = nullptr;
  if (value.GetAsDictionary(&dict)) {
    std::unique_ptr<base::DictionaryValue> out_dict(
        new base::DictionaryValue());
    for (base::DictionaryValue::Iterator it(*dict); !it.IsAtEnd();
         it.Advance()) {
      out_dict->Set(ConvertFromCamelCase(it.key(), '_'),
                    ConvertDictKeyStyle(it.value()));
    }
    return std::move(out_dict);
  }

  const base::ListValue* list = nullptr;
  if (value.GetAsList(&list)) {
    std::unique_ptr<base::ListValue> out_list(new base::ListValue());
    for (const auto& key : *list)
      out_list->Append(ConvertDictKeyStyle(key));
    return std::move(out_list);
  }

  return value.CreateDeepCopy();
}

class DevToolsTraceEndpointProxy : public TracingController::TraceDataEndpoint {
 public:
  explicit DevToolsTraceEndpointProxy(base::WeakPtr<TracingHandler> handler)
      : tracing_handler_(handler) {}

  void ReceiveTraceChunk(std::unique_ptr<std::string> chunk) override {
    if (TracingHandler* h = tracing_handler_.get())
      h->OnTraceDataCollected(std::move(chunk));
  }
  void ReceivedTraceFinalContents() override {
    if (TracingHandler* h = tracing_handler_.get())
      h->OnTraceComplete();
  }

 private:
  ~DevToolsTraceEndpointProxy() override = default;

  base::WeakPtr<TracingHandler> tracing_handler_;
};

class DevToolsStreamEndpoint : public TracingController::TraceDataEndpoint {
 public:
  explicit DevToolsStreamEndpoint(
      base::WeakPtr<TracingHandler> handler,
      const scoped_refptr<DevToolsStreamFile>& stream)
      : stream_(stream), tracing_handler_(handler) {}

  void ReceiveTraceChunk(std::unique_ptr<std::string> chunk) override {
    if (!BrowserThread::CurrentlyOn(BrowserThread::UI)) {
      GetUIThreadTaskRunner({})->PostTask(
          FROM_HERE, base::BindOnce(&DevToolsStreamEndpoint::ReceiveTraceChunk,
                                    this, std::move(chunk)));
      return;
    }

    stream_->Append(std::move(chunk));
  }

  void ReceivedTraceFinalContents() override {
    if (!BrowserThread::CurrentlyOn(BrowserThread::UI)) {
      GetUIThreadTaskRunner({})->PostTask(
          FROM_HERE,
          base::BindOnce(&DevToolsStreamEndpoint::ReceivedTraceFinalContents,
                         this));
      return;
    }
    if (TracingHandler* h = tracing_handler_.get())
      h->OnTraceToStreamComplete(stream_->handle());
  }

 private:
  ~DevToolsStreamEndpoint() override = default;

  scoped_refptr<DevToolsStreamFile> stream_;
  base::WeakPtr<TracingHandler> tracing_handler_;
};

std::string GetProcessHostHex(RenderProcessHost* host) {
  return base::StringPrintf("0x%" PRIxPTR, reinterpret_cast<uintptr_t>(host));
}

void SendProcessReadyInBrowserEvent(const base::UnguessableToken& frame_token,
                                    RenderProcessHost* host) {
  auto data = std::make_unique<base::trace_event::TracedValue>();
  data->SetString("frame", frame_token.ToString());
  data->SetString("processPseudoId", GetProcessHostHex(host));
  data->SetInteger("processId", static_cast<int>(host->GetProcess().Pid()));
  TRACE_EVENT_INSTANT1(TRACE_DISABLED_BY_DEFAULT("devtools.timeline"),
                       "ProcessReadyInBrowser", TRACE_EVENT_SCOPE_THREAD,
                       "data", std::move(data));
}

void FillFrameData(base::trace_event::TracedValue* data,
                   FrameTreeNode* node,
                   RenderFrameHostImpl* frame_host,
                   const GURL& url) {
  url::Replacements<char> strip_fragment;
  strip_fragment.ClearRef();
  data->SetString("frame", node->devtools_frame_token().ToString());
  data->SetString("url", url.ReplaceComponents(strip_fragment).spec());
  data->SetString("name", node->frame_name());
  if (node->parent()) {
    data->SetString(
        "parent",
        node->parent()->frame_tree_node()->devtools_frame_token().ToString());
  }
  if (frame_host) {
    RenderProcessHost* process_host = frame_host->GetProcess();
    const base::Process& process_handle = process_host->GetProcess();
    if (!process_handle.IsValid()) {
      data->SetString("processPseudoId", GetProcessHostHex(process_host));
      frame_host->GetProcess()->PostTaskWhenProcessIsReady(
          base::BindOnce(&SendProcessReadyInBrowserEvent,
                         node->devtools_frame_token(), process_host));
    } else {
      // Cast process id to int to be compatible with tracing.
      data->SetInteger("processId", static_cast<int>(process_handle.Pid()));
    }
  }
}

base::Optional<base::trace_event::MemoryDumpLevelOfDetail>
StringToMemoryDumpLevelOfDetail(const std::string& str) {
  if (str == Tracing::MemoryDumpLevelOfDetailEnum::Detailed)
    return {base::trace_event::MemoryDumpLevelOfDetail::DETAILED};
  if (str == Tracing::MemoryDumpLevelOfDetailEnum::Background)
    return {base::trace_event::MemoryDumpLevelOfDetail::BACKGROUND};
  if (str == Tracing::MemoryDumpLevelOfDetailEnum::Light)
    return {base::trace_event::MemoryDumpLevelOfDetail::LIGHT};
  return {};
}

void AddPidsToProcessFilter(
    const std::unordered_set<base::ProcessId>& included_process_ids,
    perfetto::TraceConfig& trace_config) {
  for (auto& data_source : *(trace_config.mutable_data_sources())) {
    auto* source_config = data_source.mutable_config();
    if (source_config->name() == tracing::mojom::kTraceEventDataSourceName) {
      for (auto& enabled_pid : included_process_ids) {
        *data_source.add_producer_name_filter() = base::StrCat(
            {tracing::mojom::kPerfettoProducerNamePrefix,
             base::NumberToString(static_cast<uint32_t>(enabled_pid))});
      }
      break;
    }
  }
}

// We currently don't support concurrent tracing sessions, but are planning to.
// For the time being, we're using this flag as a workaround to prevent devtools
// users from accidentally starting two concurrent sessions.
// TODO(eseckler): Remove once we add support for concurrent sessions to the
// perfetto backend.
static bool g_any_agent_tracing = false;

}  // namespace

class TracingHandler::TracingSession {
 public:
  TracingSession() = default;
  virtual ~TracingSession() = default;

  virtual void EnableTracing(
      const perfetto::TraceConfig& perfetto_config,
      base::OnceClosure on_recording_enabled_callback) = 0;
  virtual void AdoptStartupTracingSession(
      const perfetto::TraceConfig& perfetto_config) = 0;
  virtual void ChangeTraceConfig(
      const perfetto::TraceConfig& perfetto_config) = 0;
  virtual void DisableTracing(
      bool use_proto_format,
      const std::string& agent_label,
      const scoped_refptr<TracingController::TraceDataEndpoint>& endpoint) = 0;
  virtual void GetBufferUsage(
      base::OnceCallback<void(float percent_full,
                              size_t approximate_event_count)>
          on_buffer_usage_callback) = 0;
  virtual bool HasTracingFailed() = 0;
  virtual bool HasDataLossOccurred() = 0;

 private:
  DISALLOW_COPY_AND_ASSIGN(TracingSession);
};

class TracingHandler::PerfettoTracingSession
    : public TracingHandler::TracingSession,
      public tracing::mojom::TracingSessionClient,
      public mojo::DataPipeDrainer::Client {
 public:
  ~PerfettoTracingSession() override { DCHECK(!tracing_active_); }

  // TracingHandler::TracingSession implementation:
  void EnableTracing(const perfetto::TraceConfig& perfetto_config,
                     base::OnceClosure on_recording_enabled_callback) override {
    DCHECK(!tracing_session_host_);
    DCHECK(!tracing_active_);
    tracing_active_ = true;

    GetTracingService().BindConsumerHost(
        consumer_host_.BindNewPipeAndPassReceiver());

    on_recording_enabled_callback_ = std::move(on_recording_enabled_callback);
#if DCHECK_IS_ON()
    last_perfetto_config_ = perfetto_config;
    for (auto& data_source : *(last_perfetto_config_.mutable_data_sources())) {
      data_source.clear_producer_name_filter();
    }
#endif

    consumer_host_->EnableTracing(
        tracing_session_host_.BindNewPipeAndPassReceiver(),
        receiver_.BindNewPipeAndPassRemote(), std::move(perfetto_config),
        base::File());

    receiver_.set_disconnect_handler(
        base::BindOnce(&PerfettoTracingSession::OnTracingSessionFailed,
                       base::Unretained(this)));
    tracing_session_host_.set_disconnect_handler(
        base::BindOnce(&PerfettoTracingSession::OnTracingSessionFailed,
                       base::Unretained(this)));
  }

  void AdoptStartupTracingSession(
      const perfetto::TraceConfig& perfetto_config) override {
    // Start a perfetto tracing session, which will claim startup tracing data.
    DCHECK(!TracingController::GetInstance()->IsTracing());
    waiting_for_startup_tracing_enabled_ = true;
    EnableTracing(
        perfetto_config,
        base::BindOnce(&PerfettoTracingSession::OnStartupTracingEnabled,
                       base::Unretained(this)));
  }

  void ChangeTraceConfig(
      const perfetto::TraceConfig& perfetto_config) override {
    if (!tracing_session_host_)
      return;

#if DCHECK_IS_ON()
    // Ensure that the process filter is the only thing that gets changed
    // in a configuration during a tracing session.
    perfetto::TraceConfig config_without_filters = perfetto_config;
    for (auto& data_source : *(config_without_filters.mutable_data_sources())) {
      data_source.clear_producer_name_filter();
    }
    DCHECK(config_without_filters == last_perfetto_config_);
    last_perfetto_config_ = std::move(config_without_filters);
#endif

    tracing_session_host_->ChangeTraceConfig(perfetto_config);
  }

  void DisableTracing(bool use_proto_format,
                      const std::string& agent_label,
                      const scoped_refptr<TracingController::TraceDataEndpoint>&
                          endpoint) override {
    if (waiting_for_startup_tracing_enabled_) {
      pending_disable_tracing_task_ = base::BindOnce(
          &PerfettoTracingSession::DisableTracing, base::Unretained(this),
          use_proto_format, agent_label, endpoint);
      return;
    }
    use_proto_format_ = use_proto_format;
    agent_label_ = agent_label;
    endpoint_ = endpoint;
    tracing_active_ = false;

    if (!tracing_session_host_) {
      if (endpoint_) {
        // Will delete |this|.
        endpoint_->ReceivedTraceFinalContents();
      }
      return;
    }

    if (!use_proto_format_) {
      mojo::ScopedDataPipeProducerHandle producer_handle;
      mojo::ScopedDataPipeConsumerHandle consumer_handle;

      MojoResult result =
          mojo::CreateDataPipe(nullptr, &producer_handle, &consumer_handle);
      if (result != MOJO_RESULT_OK) {
        OnTracingSessionFailed();
        return;
      }

      drainer_ = std::make_unique<mojo::DataPipeDrainer>(
          this, std::move(consumer_handle));
      tracing_session_host_->DisableTracingAndEmitJson(
          agent_label_, std::move(producer_handle),
          /*privacy_filtering_enabled=*/false,
          base::BindOnce(&PerfettoTracingSession::OnReadBuffersComplete,
                         base::Unretained(this)));
    } else {
      // The host will call OnTracingDisabled once Perfetto has disabled
      // tracing, at which point we'll pass down the datapipe.
      tracing_session_host_->DisableTracing();
    }
  }

  void GetBufferUsage(base::OnceCallback<void(float percent_full,
                                              size_t approximate_event_count)>
                          on_buffer_usage_callback) override {
    if (!tracing_session_host_) {
      std::move(on_buffer_usage_callback).Run(0.0f, 0);
      return;
    }
    DCHECK(on_buffer_usage_callback);
    tracing_session_host_->RequestBufferUsage(base::BindOnce(
        &PerfettoTracingSession::OnBufferUsage, base::Unretained(this),
        std::move(on_buffer_usage_callback)));
  }

  bool HasTracingFailed() override {
    return tracing_active_ && !tracing_session_host_;
  }

  bool HasDataLossOccurred() override { return data_loss_; }

  // tracing::mojom::TracingSessionClient implementation:
  void OnTracingEnabled() override {
    if (on_recording_enabled_callback_) {
      std::move(on_recording_enabled_callback_).Run();
    }
  }

  void OnTracingDisabled(bool tracing_succeeded) override {
    // If we're converting to JSON, we will receive the data via
    // ConsumerHost::DisableTracingAndEmitJson().
    if (!use_proto_format_)
      return;
    if (!tracing_succeeded) {
      OnTracingSessionFailed();
      return;
    }

    DCHECK(agent_label_.empty());
    mojo::ScopedDataPipeProducerHandle producer_handle;
    mojo::ScopedDataPipeConsumerHandle consumer_handle;

    MojoResult result =
        mojo::CreateDataPipe(nullptr, &producer_handle, &consumer_handle);
    if (result != MOJO_RESULT_OK) {
      OnTracingSessionFailed();
      return;
    }

    drainer_ = std::make_unique<mojo::DataPipeDrainer>(
        this, std::move(consumer_handle));
    tracing_session_host_->ReadBuffers(
        std::move(producer_handle),
        base::BindOnce(&PerfettoTracingSession::OnReadBuffersComplete,
                       base::Unretained(this)));
  }

 private:
  void OnStartupTracingEnabled() {
    waiting_for_startup_tracing_enabled_ = false;
    if (pending_disable_tracing_task_)
      std::move(pending_disable_tracing_task_).Run();
  }

  void OnTracingSessionFailed() {
    tracing_session_host_.reset();
    receiver_.reset();
    drainer_.reset();

    if (on_recording_enabled_callback_)
      std::move(on_recording_enabled_callback_).Run();

    if (pending_disable_tracing_task_)
      std::move(pending_disable_tracing_task_).Run();

    if (endpoint_) {
      // TODO(oysteine): Signal to the client that tracing failed.
      // Will delete |this|.
      endpoint_->ReceivedTraceFinalContents();
    }
  }

  void OnBufferUsage(base::OnceCallback<void(float percent_full,
                                             size_t approximate_event_count)>
                         on_buffer_usage_callback,
                     bool success,
                     float percent_full,
                     bool data_loss) {
    if (!success) {
      std::move(on_buffer_usage_callback).Run(0.0f, 0);
      return;
    }
    data_loss_ |= data_loss;
    std::move(on_buffer_usage_callback).Run(percent_full, 0);
  }

  // mojo::DataPipeDrainer::Client implementation:
  void OnDataAvailable(const void* data, size_t num_bytes) override {
    auto data_string = std::make_unique<std::string>(
        reinterpret_cast<const char*>(data), num_bytes);
    endpoint_->ReceiveTraceChunk(std::move(data_string));
  }

  void OnDataComplete() override {
    data_complete_ = true;
    MaybeTraceComplete();
  }

  void OnReadBuffersComplete() {
    read_buffers_complete_ = true;
    MaybeTraceComplete();
  }

  void MaybeTraceComplete() {
    if (read_buffers_complete_ && data_complete_ && endpoint_) {
      // Request stats to check if data loss occurred.
      GetBufferUsage(base::BindOnce(&PerfettoTracingSession::OnFinalBufferUsage,
                                    base::Unretained(this)));
    }
  }

  void OnFinalBufferUsage(float percent_full, size_t approximate_event_count) {
    if (!endpoint_)
      return;
    // Will delete |this|.
    endpoint_->ReceivedTraceFinalContents();
  }

  mojo::Receiver<tracing::mojom::TracingSessionClient> receiver_{this};
  mojo::Remote<tracing::mojom::TracingSessionHost> tracing_session_host_;

  mojo::Remote<tracing::mojom::ConsumerHost> consumer_host_;

  bool use_proto_format_;
  std::string agent_label_;
  base::OnceClosure on_recording_enabled_callback_;
  base::OnceClosure pending_disable_tracing_task_;
  bool waiting_for_startup_tracing_enabled_ = false;
  scoped_refptr<TracingController::TraceDataEndpoint> endpoint_;
  std::unique_ptr<mojo::DataPipeDrainer> drainer_;
  bool data_complete_ = false;
  bool read_buffers_complete_ = false;
  bool tracing_active_ = false;
  bool data_loss_ = false;

#if DCHECK_IS_ON()
  perfetto::TraceConfig last_perfetto_config_;
#endif
};

TracingHandler::TracingHandler(FrameTreeNode* frame_tree_node,
                               DevToolsIOContext* io_context)
    : DevToolsDomainHandler(Tracing::Metainfo::domainName),
      io_context_(io_context),
      frame_tree_node_(frame_tree_node),
      did_initiate_recording_(false),
      return_as_stream_(false),
      gzip_compression_(false),
      buffer_usage_reporting_interval_(0) {
  bool use_video_capture_api = true;
#ifdef OS_ANDROID
  // Video capture API cannot be used on Android WebView.
  if (!CompositorImpl::IsInitialized())
    use_video_capture_api = false;
#endif
  if (use_video_capture_api) {
    video_consumer_ =
        std::make_unique<DevToolsVideoConsumer>(base::BindRepeating(
            &TracingHandler::OnFrameFromVideoConsumer, base::Unretained(this)));
  }

  auto* startup_config = tracing::TraceStartupConfig::GetInstance();
  // Check if we should adopt the startup tracing session. Only the first
  // session connected to the browser endpoint can own it.
  if (frame_tree_node_ != nullptr ||
      !startup_config->AttemptAdoptBySessionOwner(
          tracing::TraceStartupConfig::SessionOwner::kDevToolsTracingHandler)) {
    return;
  }

  session_ = std::make_unique<PerfettoTracingSession>();
  base::trace_event::TraceConfig browser_config =
      tracing::TraceStartupConfig::GetInstance()->GetTraceConfig();
  perfetto::TraceConfig perfetto_config =
      CreatePerfettoConfiguration(browser_config);
  session_->AdoptStartupTracingSession(perfetto_config);
  g_any_agent_tracing = true;
}

TracingHandler::~TracingHandler() = default;

// static
std::vector<TracingHandler*> TracingHandler::ForAgentHost(
    DevToolsAgentHostImpl* host) {
  return host->HandlersByName<TracingHandler>(Tracing::Metainfo::domainName);
}

void TracingHandler::SetRenderer(int process_host_id,
                                 RenderFrameHostImpl* frame_host) {
  if (!video_consumer_ || !frame_host)
    return;
  video_consumer_->SetFrameSinkId(
      frame_host->GetRenderWidgetHost()->GetFrameSinkId());
}

void TracingHandler::Wire(UberDispatcher* dispatcher) {
  frontend_.reset(new Tracing::Frontend(dispatcher->channel()));
  Tracing::Dispatcher::wire(dispatcher, this);
}

Response TracingHandler::Disable() {
  if (session_)
    StopTracing(nullptr, "");
  return Response::Success();
}

namespace {
class TracingNotification : public crdtp::Serializable {
 public:
  explicit TracingNotification(std::string json) : json_(std::move(json)) {}

  void AppendSerialized(std::vector<uint8_t>* out) const override {
    crdtp::Status status =
        crdtp::json::ConvertJSONToCBOR(crdtp::SpanFrom(json_), out);
    DCHECK(status.ok()) << status.ToASCIIString();
  }

 private:
  std::string json_;
};
}  // namespace

void TracingHandler::OnTraceDataCollected(
    std::unique_ptr<std::string> trace_fragment) {
  const std::string valid_trace_fragment =
      UpdateTraceDataBuffer(*trace_fragment);
  if (valid_trace_fragment.empty())
    return;

  // Hand-craft protocol notification message so we can substitute JSON
  // that we already got as string as a bare object, not a quoted string.
  std::string message(
      "{ \"method\": \"Tracing.dataCollected\", \"params\": { \"value\": [");
  const size_t messageSuffixSize = 10;
  message.reserve(message.size() + valid_trace_fragment.size() +
                  messageSuffixSize - trace_data_buffer_state_.offset);
  message.append(valid_trace_fragment.c_str() +
                 trace_data_buffer_state_.offset);
  message += "] } }";
  frontend_->sendRawNotification(
      std::make_unique<TracingNotification>(std::move(message)));
}

void TracingHandler::OnTraceComplete() {
  if (!trace_data_buffer_state_.data.empty())
    OnTraceDataCollected(std::make_unique<std::string>(""));

  DCHECK(trace_data_buffer_state_.data.empty());
  DCHECK_EQ(0u, trace_data_buffer_state_.pos);
  DCHECK_EQ(0, trace_data_buffer_state_.open_braces);
  DCHECK(!trace_data_buffer_state_.in_string);
  DCHECK(!trace_data_buffer_state_.slashed);

  bool data_loss = session_->HasDataLossOccurred();
  session_.reset();
  frontend_->TracingComplete(data_loss);
}

std::string TracingHandler::UpdateTraceDataBuffer(
    const std::string& trace_fragment) {
  size_t end = 0;
  size_t last_open = 0;
  TraceDataBufferState& state = trace_data_buffer_state_;
  state.offset = 0;
  bool update_offset = state.open_braces == 0;
  for (; state.pos < trace_fragment.size(); ++state.pos) {
    char c = trace_fragment[state.pos];
    switch (c) {
      case '{':
        if (!state.in_string && !state.slashed) {
          state.open_braces++;
          if (state.open_braces == 1) {
            last_open = state.data.size() + state.pos;
            if (update_offset) {
              state.offset = last_open;
              update_offset = false;
            }
          }
        }
        break;
      case '}':
        if (!state.in_string && !state.slashed) {
          DCHECK_GT(state.open_braces, 0);
          state.open_braces--;
          if (state.open_braces == 0)
            end = state.data.size() + state.pos + 1;
        }
        break;
      case '"':
        if (!state.slashed)
          state.in_string = !state.in_string;
        break;
      case 'u':
        if (state.slashed)
          state.pos += 4;
        break;
    }

    if (state.in_string && c == '\\') {
      state.slashed = !state.slashed;
    } else {
      state.slashed = false;
    }
  }

  // Next starting position is usually 0 except when we are in the middle of
  // processing a unicode character, i.e. \uxxxx.
  state.pos -= trace_fragment.size();

  std::string complete_str = state.data + trace_fragment;
  state.data = complete_str.substr(std::max(end, last_open));

  complete_str.resize(end);
  return complete_str;
}

void TracingHandler::OnTraceToStreamComplete(const std::string& stream_handle) {
  bool data_loss = session_->HasDataLossOccurred();
  session_.reset();
  std::string stream_format = (proto_format_ ? Tracing::StreamFormatEnum::Proto
                                             : Tracing::StreamFormatEnum::Json);
  std::string stream_compression =
      (gzip_compression_ ? Tracing::StreamCompressionEnum::Gzip
                         : Tracing::StreamCompressionEnum::None);
  frontend_->TracingComplete(data_loss, stream_handle, stream_format,
                             stream_compression);
}

void TracingHandler::Start(Maybe<std::string> categories,
                           Maybe<std::string> options,
                           Maybe<double> buffer_usage_reporting_interval,
                           Maybe<std::string> transfer_mode,
                           Maybe<std::string> transfer_format,
                           Maybe<std::string> transfer_compression,
                           Maybe<Tracing::TraceConfig> config,
                           Maybe<Binary> perfetto_config,
                           std::unique_ptr<StartCallback> callback) {
  bool return_as_stream = transfer_mode.fromMaybe("") ==
                          Tracing::Start::TransferModeEnum::ReturnAsStream;
  bool gzip_compression = transfer_compression.fromMaybe("") ==
                          Tracing::StreamCompressionEnum::Gzip;
  bool proto_format =
      transfer_format.fromMaybe("") == Tracing::StreamFormatEnum::Proto;

  if (proto_format && !return_as_stream) {
    callback->sendFailure(Response::ServerError(
        "Proto format is only supported when using stream transfer mode."));
    return;
  }

  if (IsTracing()) {
    if (!did_initiate_recording_ && IsStartupTracingActive()) {
      // If tracing is already running because it was initiated by startup
      // tracing, honor the transfer mode/format update, as that's the only way
      // for the client to communicate it.
      return_as_stream_ = return_as_stream;
      gzip_compression_ = gzip_compression;
      proto_format_ = proto_format;
    }
    callback->sendFailure(Response::ServerError(
        "Tracing has already been started (possibly in another tab)."));
    return;
  }

  if (config.isJust() && (categories.isJust() || options.isJust())) {
    callback->sendFailure(Response::InvalidParams(
        "Either trace config (preferred), or categories+options should be "
        "specified, but not both."));
    return;
  }

  did_initiate_recording_ = true;
  return_as_stream_ = return_as_stream;
  gzip_compression_ = gzip_compression;
  proto_format_ = proto_format;
  buffer_usage_reporting_interval_ =
      buffer_usage_reporting_interval.fromMaybe(0);

  if (perfetto_config.isJust()) {
    bool parsed = trace_config_.ParseFromArray(
        perfetto_config.fromJust().data(), perfetto_config.fromJust().size());
    if (!parsed) {
      callback->sendFailure(Response::InvalidParams(
          "Couldn't parse the supplied perfettoConfig."));
      return;
    }
  } else {
    base::trace_event::TraceConfig browser_config =
        base::trace_event::TraceConfig();
    if (config.isJust()) {
      std::unique_ptr<base::Value> value = protocol::toBaseValue(
          protocol::ValueTypeConverter<Tracing::TraceConfig>::ToValue(
              *config.fromJust())
              .get(),
          1000);
      if (value && value->is_dict()) {
        browser_config = GetTraceConfigFromDevToolsConfig(
            *static_cast<base::DictionaryValue*>(value.get()));
      }
    } else if (categories.isJust() || options.isJust()) {
      browser_config = base::trace_event::TraceConfig(categories.fromMaybe(""),
                                                      options.fromMaybe(""));
    }
    trace_config_ = CreatePerfettoConfiguration(browser_config);
  }

  // GPU process id can only be retrieved on IO thread. Do some thread hopping.
  GetIOThreadTaskRunner({})->PostTaskAndReplyWithResult(
      FROM_HERE, base::BindOnce([]() {
        GpuProcessHost* gpu_process_host =
            GpuProcessHost::Get(GPU_PROCESS_KIND_SANDBOXED,
                                /* force_create */ false);
        return gpu_process_host ? gpu_process_host->process_id()
                                : base::kNullProcessId;
      }),
      base::BindOnce(&TracingHandler::StartTracingWithGpuPid,
                     weak_factory_.GetWeakPtr(), std::move(callback)));
}

void TracingHandler::StartTracingWithGpuPid(
    std::unique_ptr<StartCallback> callback,
    base::ProcessId gpu_pid) {
  // Check if tracing was stopped in mid-air.
  if (!did_initiate_recording_) {
    callback->sendFailure(Response::ServerError(
        "Tracing was stopped before start has been completed."));
    return;
  }

  SetupProcessFilter(gpu_pid, nullptr);

  session_ = std::make_unique<PerfettoTracingSession>();
  session_->EnableTracing(
      trace_config_,
      base::BindOnce(&TracingHandler::OnRecordingEnabled,
                     weak_factory_.GetWeakPtr(), std::move(callback)));
  g_any_agent_tracing = true;
}

perfetto::TraceConfig TracingHandler::CreatePerfettoConfiguration(
    const base::trace_event::TraceConfig& browser_config) {
  return tracing::GetDefaultPerfettoConfig(
      browser_config,
      /*privacy_filtering_enabled=*/false,
      /*convert_to_legacy_json=*/false,
      perfetto::protos::gen::ChromeConfig::USER_INITIATED);
}

void TracingHandler::SetupProcessFilter(
    base::ProcessId gpu_pid,
    RenderFrameHost* new_render_frame_host) {
  if (!frame_tree_node_)
    return;

  base::ProcessId browser_pid = base::Process::Current().Pid();
  std::unordered_set<base::ProcessId> included_process_ids({browser_pid});

  if (gpu_pid != base::kNullProcessId)
    included_process_ids.insert(gpu_pid);

  if (new_render_frame_host)
    AppendProcessId(new_render_frame_host, &included_process_ids);

  for (FrameTreeNode* node :
       frame_tree_node_->frame_tree()->SubtreeNodes(frame_tree_node_)) {
    RenderFrameHost* frame_host = node->current_frame_host();
    if (frame_host)
      AppendProcessId(frame_host, &included_process_ids);
  }

  AddPidsToProcessFilter(included_process_ids, trace_config_);
}

void TracingHandler::AppendProcessId(
    RenderFrameHost* render_frame_host,
    std::unordered_set<base::ProcessId>* process_set) {
  RenderProcessHost* process_host = render_frame_host->GetProcess();
  if (process_host->GetProcess().IsValid()) {
    process_set->insert(process_host->GetProcess().Pid());
  } else {
    process_host->PostTaskWhenProcessIsReady(
        base::BindOnce(&TracingHandler::OnProcessReady,
                       weak_factory_.GetWeakPtr(), process_host));
  }
}

void TracingHandler::OnProcessReady(RenderProcessHost* process_host) {
  if (!did_initiate_recording_)
    return;
  std::unordered_set<base::ProcessId> included_process_ids(
      {process_host->GetProcess().Pid()});

  AddPidsToProcessFilter(included_process_ids, trace_config_);
  session_->ChangeTraceConfig(trace_config_);
}

Response TracingHandler::End() {
  if (!session_)
    return Response::ServerError("Tracing is not started");

  if (session_->HasTracingFailed())
    return Response::ServerError("Tracing failed");

  scoped_refptr<TracingController::TraceDataEndpoint> endpoint;
  if (return_as_stream_) {
    endpoint = new DevToolsStreamEndpoint(
        weak_factory_.GetWeakPtr(),
        DevToolsStreamFile::Create(
            io_context_, gzip_compression_ || proto_format_ /* binary */));
    if (gzip_compression_) {
      endpoint = TracingControllerImpl::CreateCompressedStringEndpoint(
          endpoint, true /* compress_with_background_priority */);
    }
    StopTracing(endpoint, "");
  } else {
    // Reset the trace data buffer state.
    trace_data_buffer_state_ = TracingHandler::TraceDataBufferState();
    endpoint = new DevToolsTraceEndpointProxy(weak_factory_.GetWeakPtr());
    StopTracing(endpoint, tracing::mojom::kChromeTraceEventLabel);
  }

  return Response::Success();
}

void TracingHandler::GetCategories(
    std::unique_ptr<GetCategoriesCallback> callback) {
  // TODO(eseckler): Support this via the perfetto service too.
  TracingController::GetInstance()->GetCategories(
      base::BindOnce(&TracingHandler::OnCategoriesReceived,
                     weak_factory_.GetWeakPtr(), std::move(callback)));
}

void TracingHandler::OnRecordingEnabled(
    std::unique_ptr<StartCallback> callback) {
  if (!did_initiate_recording_) {
    callback->sendFailure(Response::ServerError(
        "Tracing was stopped before start has been completed."));
    return;
  }

  EmitFrameTree();
  callback->sendSuccess();

  SetupTimer(buffer_usage_reporting_interval_);

  bool screenshot_enabled;
  TRACE_EVENT_CATEGORY_GROUP_ENABLED(
      TRACE_DISABLED_BY_DEFAULT("devtools.screenshot"), &screenshot_enabled);
  if (video_consumer_ && screenshot_enabled) {
    // Reset number of screenshots received, each time tracing begins.
    number_of_screenshots_from_video_consumer_ = 0;
    video_consumer_->SetMinAndMaxFrameSize(kMinFrameSize, kMaxFrameSize);
    video_consumer_->StartCapture();
  }
}

void TracingHandler::OnBufferUsage(float percent_full,
                                   size_t approximate_event_count) {
  if (!did_initiate_recording_)
    return;
  // TODO(crbug426117): remove set_value once all clients have switched to
  // the new interface of the event.
  frontend_->BufferUsage(percent_full, approximate_event_count, percent_full);
}

void TracingHandler::OnCategoriesReceived(
    std::unique_ptr<GetCategoriesCallback> callback,
    const std::set<std::string>& category_set) {
  auto categories = std::make_unique<protocol::Array<std::string>>(
      category_set.begin(), category_set.end());
  callback->sendSuccess(std::move(categories));
}

void TracingHandler::RequestMemoryDump(
    Maybe<bool> deterministic,
    Maybe<std::string> level_of_detail,
    std::unique_ptr<RequestMemoryDumpCallback> callback) {
  if (!IsTracing()) {
    callback->sendFailure(Response::ServerError("Tracing is not started"));
    return;
  }

  base::Optional<base::trace_event::MemoryDumpLevelOfDetail> memory_detail =
      StringToMemoryDumpLevelOfDetail(level_of_detail.fromMaybe(
          Tracing::MemoryDumpLevelOfDetailEnum::Detailed));

  if (!memory_detail) {
    callback->sendFailure(
        Response::ServerError("Invalid levelOfDetail specified."));
    return;
  }

  auto determinism = deterministic.fromMaybe(false)
                         ? base::trace_event::MemoryDumpDeterminism::FORCE_GC
                         : base::trace_event::MemoryDumpDeterminism::NONE;

  auto on_memory_dump_finished =
      base::BindOnce(&TracingHandler::OnMemoryDumpFinished,
                     weak_factory_.GetWeakPtr(), std::move(callback));

  memory_instrumentation::MemoryInstrumentation::GetInstance()
      ->RequestGlobalDumpAndAppendToTrace(
          base::trace_event::MemoryDumpType::EXPLICITLY_TRIGGERED,
          *memory_detail, determinism, std::move(on_memory_dump_finished));
}

void TracingHandler::OnMemoryDumpFinished(
    std::unique_ptr<RequestMemoryDumpCallback> callback,
    bool success,
    uint64_t dump_id) {
  callback->sendSuccess(base::StringPrintf("0x%" PRIx64, dump_id), success);
}

void TracingHandler::OnFrameFromVideoConsumer(
    scoped_refptr<media::VideoFrame> frame) {
  const SkBitmap skbitmap = DevToolsVideoConsumer::GetSkBitmapFromFrame(frame);

  base::TimeTicks reference_time = *frame->metadata()->reference_time;

  TRACE_EVENT_OBJECT_SNAPSHOT_WITH_ID_AND_TIMESTAMP(
      TRACE_DISABLED_BY_DEFAULT("devtools.screenshot"), "Screenshot", 1,
      reference_time, std::make_unique<DevToolsTraceableScreenshot>(skbitmap));

  ++number_of_screenshots_from_video_consumer_;
  DCHECK(video_consumer_);
  if (number_of_screenshots_from_video_consumer_ >=
      DevToolsTraceableScreenshot::kMaximumNumberOfScreenshots) {
    video_consumer_->StopCapture();
  }
}

Response TracingHandler::RecordClockSyncMarker(const std::string& sync_id) {
  if (!IsTracing())
    return Response::ServerError("Tracing is not started");
  TRACE_EVENT_CLOCK_SYNC_RECEIVER(sync_id);
  return Response::Success();
}

void TracingHandler::SetupTimer(double usage_reporting_interval) {
  if (usage_reporting_interval == 0)
    return;

  if (usage_reporting_interval < kMinimumReportingInterval)
    usage_reporting_interval = kMinimumReportingInterval;

  base::TimeDelta interval =
      base::TimeDelta::FromMilliseconds(std::ceil(usage_reporting_interval));
  buffer_usage_poll_timer_.reset(new base::RepeatingTimer());
  buffer_usage_poll_timer_->Start(
      FROM_HERE, interval,
      base::BindRepeating(&TracingHandler::UpdateBufferUsage,
                          weak_factory_.GetWeakPtr()));
}

void TracingHandler::UpdateBufferUsage() {
  session_->GetBufferUsage(base::BindOnce(&TracingHandler::OnBufferUsage,
                                          weak_factory_.GetWeakPtr()));
}

void TracingHandler::StopTracing(
    const scoped_refptr<TracingController::TraceDataEndpoint>& endpoint,
    const std::string& agent_label) {
  DCHECK(session_);
  buffer_usage_poll_timer_.reset();
  session_->DisableTracing(proto_format_, agent_label, endpoint);
  did_initiate_recording_ = false;
  g_any_agent_tracing = false;
  if (video_consumer_)
    video_consumer_->StopCapture();
}

bool TracingHandler::IsTracing() const {
  return TracingController::GetInstance()->IsTracing() || g_any_agent_tracing;
}

void TracingHandler::EmitFrameTree() {
  auto data = std::make_unique<base::trace_event::TracedValue>();
  if (frame_tree_node_) {
    data->SetInteger("frameTreeNodeId", frame_tree_node_->frame_tree_node_id());
    data->SetBoolean("persistentIds", true);
    data->BeginArray("frames");
    FrameTree::NodeRange subtree =
        frame_tree_node_->frame_tree()->SubtreeNodes(frame_tree_node_);
    for (FrameTreeNode* node : subtree) {
      data->BeginDictionary();
      FillFrameData(data.get(), node, node->current_frame_host(),
                    node->current_url());
      data->EndDictionary();
    }
    data->EndArray();
  }
  TRACE_EVENT_INSTANT1(TRACE_DISABLED_BY_DEFAULT("devtools.timeline"),
                       "TracingStartedInBrowser", TRACE_EVENT_SCOPE_THREAD,
                       "data", std::move(data));
}

void TracingHandler::ReadyToCommitNavigation(
    NavigationRequest* navigation_request) {
  if (!did_initiate_recording_)
    return;
  auto data = std::make_unique<base::trace_event::TracedValue>();
  FillFrameData(data.get(), navigation_request->frame_tree_node(),
                navigation_request->GetRenderFrameHost(),
                navigation_request->GetURL());
  TRACE_EVENT_INSTANT1(TRACE_DISABLED_BY_DEFAULT("devtools.timeline"),
                       "FrameCommittedInBrowser", TRACE_EVENT_SCOPE_THREAD,
                       "data", std::move(data));

  SetupProcessFilter(base::kNullProcessId,
                     navigation_request->GetRenderFrameHost());
  session_->ChangeTraceConfig(trace_config_);
}

void TracingHandler::FrameDeleted(RenderFrameHostImpl* frame_host) {
  if (!did_initiate_recording_)
    return;
  auto data = std::make_unique<base::trace_event::TracedValue>();
  data->SetString(
      "frame",
      frame_host->frame_tree_node()->devtools_frame_token().ToString());
  TRACE_EVENT_INSTANT1(TRACE_DISABLED_BY_DEFAULT("devtools.timeline"),
                       "FrameDeletedInBrowser", TRACE_EVENT_SCOPE_THREAD,
                       "data", std::move(data));
}

// static
bool TracingHandler::IsStartupTracingActive() {
  return ::tracing::TraceStartupConfig::GetInstance()->IsEnabled();
}

// static
base::trace_event::TraceConfig TracingHandler::GetTraceConfigFromDevToolsConfig(
    const base::DictionaryValue& devtools_config) {
  std::unique_ptr<base::Value> value = ConvertDictKeyStyle(devtools_config);
  DCHECK(value && value->is_dict());
  std::unique_ptr<base::DictionaryValue> tracing_dict(
      static_cast<base::DictionaryValue*>(value.release()));

  std::string mode;
  if (tracing_dict->GetString(kRecordModeParam, &mode))
    tracing_dict->SetString(kRecordModeParam, ConvertFromCamelCase(mode, '-'));

  return base::trace_event::TraceConfig(*tracing_dict);
}

}  // namespace protocol
}  // namespace content