// 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 "extensions/browser/extension_function_dispatcher.h"

#include <utility>

#include "base/bind.h"
#include "base/json/json_string_value_serializer.h"
#include "base/lazy_instance.h"
#include "base/logging.h"
#include "base/macros.h"
#include "base/memory/ref_counted.h"
#include "base/metrics/histogram_macros.h"
#include "base/metrics/sparse_histogram.h"
#include "base/process/process.h"
#include "base/profiler/scoped_profile.h"
#include "base/scoped_observer.h"
#include "base/values.h"
#include "build/build_config.h"
#include "content/public/browser/browser_thread.h"
#include "content/public/browser/render_frame_host.h"
#include "content/public/browser/render_process_host.h"
#include "content/public/browser/render_process_host_observer.h"
#include "content/public/browser/render_view_host.h"
#include "content/public/browser/user_metrics.h"
#include "content/public/browser/web_contents.h"
#include "content/public/browser/web_contents_observer.h"
#include "content/public/common/result_codes.h"
#include "extensions/browser/api_activity_monitor.h"
#include "extensions/browser/extension_function_registry.h"
#include "extensions/browser/extension_registry.h"
#include "extensions/browser/extension_system.h"
#include "extensions/browser/extensions_browser_client.h"
#include "extensions/browser/io_thread_extension_message_filter.h"
#include "extensions/browser/process_manager.h"
#include "extensions/browser/process_map.h"
#include "extensions/browser/quota_service.h"
#include "extensions/common/extension_api.h"
#include "extensions/common/extension_messages.h"
#include "extensions/common/extension_set.h"
#include "extensions/common/extensions_client.h"
#include "ipc/ipc_message.h"
#include "ipc/ipc_message_macros.h"

using content::BrowserThread;
using content::RenderViewHost;

namespace extensions {
namespace {

// Notifies the ApiActivityMonitor that an extension API function has been
// called. May be called from any thread.
void NotifyApiFunctionCalled(const std::string& extension_id,
                             const std::string& api_name,
                             std::unique_ptr<base::ListValue> args,
                             content::BrowserContext* browser_context) {
  // The ApiActivityMonitor can only be accessed from the main (UI) thread. If
  // we're running on the wrong thread, re-dispatch from the main thread.
  if (!BrowserThread::CurrentlyOn(BrowserThread::UI)) {
    BrowserThread::PostTask(BrowserThread::UI,
                            FROM_HERE,
                            base::Bind(&NotifyApiFunctionCalled,
                                       extension_id,
                                       api_name,
                                       base::Passed(&args),
                                       browser_context));
    return;
  }
  // The BrowserContext may become invalid after the task above is posted.
  if (!ExtensionsBrowserClient::Get()->IsValidContext(browser_context))
    return;

  ApiActivityMonitor* monitor =
      ExtensionsBrowserClient::Get()->GetApiActivityMonitor(browser_context);
  if (monitor)
    monitor->OnApiFunctionCalled(extension_id, api_name, std::move(args));
}

// Separate copy of ExtensionAPI used for IO thread extension functions. We need
// this because ExtensionAPI has mutable data. It should be possible to remove
// this once all the extension APIs are updated to the feature system.
struct Static {
  Static() : api(ExtensionAPI::CreateWithDefaultConfiguration()) {}
  std::unique_ptr<ExtensionAPI> api;
};
base::LazyInstance<Static> g_global_io_data = LAZY_INSTANCE_INITIALIZER;

// Kills the specified process because it sends us a malformed message.
// Track the specific function's |histogram_value|, as this may indicate a bug
// in that API's implementation on the renderer.
void KillBadMessageSender(const base::Process& process,
                          functions::HistogramValue histogram_value) {
  // The renderer has done validation before sending extension api requests.
  // Therefore, we should never receive a request that is invalid in a way
  // that JSON validation in the renderer should have caught. It could be an
  // attacker trying to exploit the browser, so we crash the renderer instead.
  LOG(ERROR) << "Terminating renderer because of malformed extension message.";
  if (content::RenderProcessHost::run_renderer_in_process()) {
    // In single process mode it is better if we don't suicide but just crash.
    CHECK(false);
    return;
  }

  NOTREACHED();
  content::RecordAction(base::UserMetricsAction("BadMessageTerminate_EFD"));
  UMA_HISTOGRAM_ENUMERATION("Extensions.BadMessageFunctionName",
                            histogram_value, functions::ENUM_BOUNDARY);
  if (process.IsValid())
    process.Terminate(content::RESULT_CODE_KILLED_BAD_MESSAGE, false);
}

void KillBadMessageSenderRPH(content::RenderProcessHost* sender_process_host,
                             functions::HistogramValue histogram_value) {
  base::Process peer_process =
      content::RenderProcessHost::run_renderer_in_process()
          ? base::Process::Current()
          : base::Process::DeprecatedGetProcessFromHandle(
                sender_process_host->GetHandle());
  KillBadMessageSender(peer_process, histogram_value);
}

void CommonResponseCallback(IPC::Sender* ipc_sender,
                            int routing_id,
                            const base::Process& peer_process,
                            int request_id,
                            ExtensionFunction::ResponseType type,
                            const base::ListValue& results,
                            const std::string& error,
                            functions::HistogramValue histogram_value) {
  DCHECK(ipc_sender);

  if (type == ExtensionFunction::BAD_MESSAGE) {
    KillBadMessageSender(peer_process, histogram_value);
    return;
  }

  ipc_sender->Send(new ExtensionMsg_Response(
      routing_id, request_id, type == ExtensionFunction::SUCCEEDED, results,
      error));
}

void IOThreadResponseCallback(
    const base::WeakPtr<IOThreadExtensionMessageFilter>& ipc_sender,
    int routing_id,
    int request_id,
    ExtensionFunction::ResponseType type,
    const base::ListValue& results,
    const std::string& error,
    functions::HistogramValue histogram_value) {
  if (!ipc_sender.get())
    return;

  base::Process peer_process =
      base::Process::DeprecatedGetProcessFromHandle(ipc_sender->PeerHandle());
  CommonResponseCallback(ipc_sender.get(), routing_id, peer_process, request_id,
                         type, results, error, histogram_value);
}

}  // namespace

class ExtensionFunctionDispatcher::UIThreadResponseCallbackWrapper
    : public content::WebContentsObserver {
 public:
  UIThreadResponseCallbackWrapper(
      const base::WeakPtr<ExtensionFunctionDispatcher>& dispatcher,
      content::RenderFrameHost* render_frame_host)
      : content::WebContentsObserver(
            content::WebContents::FromRenderFrameHost(render_frame_host)),
        dispatcher_(dispatcher),
        render_frame_host_(render_frame_host),
        weak_ptr_factory_(this) {
  }

  ~UIThreadResponseCallbackWrapper() override {}

  // content::WebContentsObserver overrides.
  void RenderFrameDeleted(
      content::RenderFrameHost* render_frame_host) override {
    DCHECK_CURRENTLY_ON(BrowserThread::UI);
    if (render_frame_host != render_frame_host_)
      return;

    if (dispatcher_.get()) {
      dispatcher_->ui_thread_response_callback_wrappers_
          .erase(render_frame_host);
    }

    delete this;
  }

  ExtensionFunction::ResponseCallback CreateCallback(int request_id) {
    return base::Bind(
        &UIThreadResponseCallbackWrapper::OnExtensionFunctionCompleted,
        weak_ptr_factory_.GetWeakPtr(),
        request_id);
  }

 private:
  void OnExtensionFunctionCompleted(int request_id,
                                    ExtensionFunction::ResponseType type,
                                    const base::ListValue& results,
                                    const std::string& error,
                                    functions::HistogramValue histogram_value) {
    base::Process process =
        content::RenderProcessHost::run_renderer_in_process()
            ? base::Process::Current()
            : base::Process::DeprecatedGetProcessFromHandle(
                  render_frame_host_->GetProcess()->GetHandle());
    CommonResponseCallback(render_frame_host_,
                           render_frame_host_->GetRoutingID(),
                           process, request_id, type, results, error,
                           histogram_value);
  }

  base::WeakPtr<ExtensionFunctionDispatcher> dispatcher_;
  content::RenderFrameHost* render_frame_host_;
  base::WeakPtrFactory<UIThreadResponseCallbackWrapper> weak_ptr_factory_;

  DISALLOW_COPY_AND_ASSIGN(UIThreadResponseCallbackWrapper);
};

class ExtensionFunctionDispatcher::UIThreadWorkerResponseCallbackWrapper
    : public content::RenderProcessHostObserver {
 public:
  UIThreadWorkerResponseCallbackWrapper(
      const base::WeakPtr<ExtensionFunctionDispatcher>& dispatcher,
      int render_process_id,
      int worker_thread_id)
      : dispatcher_(dispatcher),
        observer_(this),
        render_process_id_(render_process_id),
        worker_thread_id_(worker_thread_id),
        weak_ptr_factory_(this) {
    observer_.Add(content::RenderProcessHost::FromID(render_process_id_));
    DCHECK(ExtensionsClient::Get()
               ->ExtensionAPIEnabledInExtensionServiceWorkers());
  }

  ~UIThreadWorkerResponseCallbackWrapper() override {}

  // content::RenderProcessHostObserver override.
  void RenderProcessExited(content::RenderProcessHost* rph,
                           base::TerminationStatus status,
                           int exit_code) override {
    CleanUp();
  }

  // content::RenderProcessHostObserver override.
  void RenderProcessHostDestroyed(content::RenderProcessHost* rph) override {
    CleanUp();
  }

  ExtensionFunction::ResponseCallback CreateCallback(int request_id) {
    return base::Bind(
        &UIThreadWorkerResponseCallbackWrapper::OnExtensionFunctionCompleted,
        weak_ptr_factory_.GetWeakPtr(), request_id);
  }

 private:
  void CleanUp() {
    DCHECK_CURRENTLY_ON(BrowserThread::UI);
    if (dispatcher_)
      dispatcher_->RemoveWorkerCallbacksForProcess(render_process_id_);
    // Note: we are deleted here!
  }

  void OnExtensionFunctionCompleted(int request_id,
                                    ExtensionFunction::ResponseType type,
                                    const base::ListValue& results,
                                    const std::string& error,
                                    functions::HistogramValue histogram_value) {
    content::RenderProcessHost* sender =
        content::RenderProcessHost::FromID(render_process_id_);
    if (type == ExtensionFunction::BAD_MESSAGE) {
      KillBadMessageSenderRPH(sender, histogram_value);
      return;
    }
    DCHECK(sender);
    sender->Send(new ExtensionMsg_ResponseWorker(
        worker_thread_id_, request_id, type == ExtensionFunction::SUCCEEDED,
        results, error));
  }

  base::WeakPtr<ExtensionFunctionDispatcher> dispatcher_;
  ScopedObserver<content::RenderProcessHost,
                 UIThreadWorkerResponseCallbackWrapper>
      observer_;
  const int render_process_id_;
  const int worker_thread_id_;
  base::WeakPtrFactory<UIThreadWorkerResponseCallbackWrapper> weak_ptr_factory_;

  DISALLOW_COPY_AND_ASSIGN(UIThreadWorkerResponseCallbackWrapper);
};

struct ExtensionFunctionDispatcher::WorkerResponseCallbackMapKey {
  WorkerResponseCallbackMapKey(int render_process_id, int embedded_worker_id)
      : render_process_id(render_process_id),
        embedded_worker_id(embedded_worker_id) {}

  bool operator<(const WorkerResponseCallbackMapKey& other) const {
    return std::tie(render_process_id, embedded_worker_id) <
           std::tie(other.render_process_id, other.embedded_worker_id);
  }

  int render_process_id;
  int embedded_worker_id;
};

WindowController*
ExtensionFunctionDispatcher::Delegate::GetExtensionWindowController() const {
  return nullptr;
}

content::WebContents*
ExtensionFunctionDispatcher::Delegate::GetAssociatedWebContents() const {
  return nullptr;
}

content::WebContents*
ExtensionFunctionDispatcher::Delegate::GetVisibleWebContents() const {
  return GetAssociatedWebContents();
}

bool ExtensionFunctionDispatcher::OverrideFunction(
    const std::string& name, ExtensionFunctionFactory factory) {
  return ExtensionFunctionRegistry::GetInstance()->OverrideFunction(name,
                                                                    factory);
}

// static
void ExtensionFunctionDispatcher::DispatchOnIOThread(
    InfoMap* extension_info_map,
    void* profile_id,
    int render_process_id,
    base::WeakPtr<IOThreadExtensionMessageFilter> ipc_sender,
    int routing_id,
    const ExtensionHostMsg_Request_Params& params) {
  const Extension* extension =
      extension_info_map->extensions().GetByID(params.extension_id);

  ExtensionFunction::ResponseCallback callback(
      base::Bind(&IOThreadResponseCallback, ipc_sender, routing_id,
                 params.request_id));

  scoped_refptr<ExtensionFunction> function(
      CreateExtensionFunction(params,
                              extension,
                              render_process_id,
                              extension_info_map->process_map(),
                              g_global_io_data.Get().api.get(),
                              profile_id,
                              callback));
  if (!function.get())
    return;

  IOThreadExtensionFunction* function_io =
      function->AsIOThreadExtensionFunction();
  if (!function_io) {
    NOTREACHED();
    return;
  }
  function_io->set_ipc_sender(ipc_sender, routing_id);
  function_io->set_extension_info_map(extension_info_map);
  if (extension) {
    function->set_include_incognito(
        extension_info_map->IsIncognitoEnabled(extension->id()));
  }

  if (!CheckPermissions(function.get(), params, callback))
    return;

  if (!extension) {
    // Skip all of the UMA, quota, event page, activity logging stuff if there
    // isn't an extension, e.g. if the function call was from WebUI.
    function->RunWithValidation()->Execute();
    return;
  }

  QuotaService* quota = extension_info_map->GetQuotaService();
  std::string violation_error = quota->Assess(extension->id(),
                                              function.get(),
                                              &params.arguments,
                                              base::TimeTicks::Now());
  if (violation_error.empty()) {
    std::unique_ptr<base::ListValue> args(params.arguments.DeepCopy());
    NotifyApiFunctionCalled(extension->id(), params.name, std::move(args),
                            static_cast<content::BrowserContext*>(profile_id));
    UMA_HISTOGRAM_SPARSE_SLOWLY("Extensions.FunctionCalls",
                                function->histogram_value());
    tracked_objects::ScopedProfile scoped_profile(
        FROM_HERE_WITH_EXPLICIT_FUNCTION(function->name()),
        tracked_objects::ScopedProfile::ENABLED);
    base::ElapsedTimer timer;
    function->RunWithValidation()->Execute();
    // TODO(devlin): Once we have a baseline metric for how long functions take,
    // we can create a handful of buckets and record the function name so that
    // we can find what the fastest/slowest are.
    // Note: Many functions execute finish asynchronously, so this time is not
    // always a representation of total time taken. See also
    // Extensions.Functions.TotalExecutionTime.
    UMA_HISTOGRAM_TIMES("Extensions.Functions.SynchronousExecutionTime",
                        timer.Elapsed());
  } else {
    function->OnQuotaExceeded(violation_error);
  }
}

ExtensionFunctionDispatcher::ExtensionFunctionDispatcher(
    content::BrowserContext* browser_context)
    : browser_context_(browser_context), delegate_(nullptr) {}

ExtensionFunctionDispatcher::~ExtensionFunctionDispatcher() {
}

void ExtensionFunctionDispatcher::Dispatch(
    const ExtensionHostMsg_Request_Params& params,
    content::RenderFrameHost* render_frame_host,
    int render_process_id) {
  if (render_frame_host) {
    // Extension API from a non Service Worker context, e.g. extension page,
    // background page, content script.
    UIThreadResponseCallbackWrapperMap::const_iterator iter =
        ui_thread_response_callback_wrappers_.find(render_frame_host);
    UIThreadResponseCallbackWrapper* callback_wrapper = nullptr;
    if (iter == ui_thread_response_callback_wrappers_.end()) {
      callback_wrapper =
          new UIThreadResponseCallbackWrapper(AsWeakPtr(), render_frame_host);
      ui_thread_response_callback_wrappers_[render_frame_host] =
          callback_wrapper;
    } else {
      callback_wrapper = iter->second;
    }
    DispatchWithCallbackInternal(
        params, render_frame_host, render_process_id,
        callback_wrapper->CreateCallback(params.request_id));
  } else {
    // Extension API from Service Worker.
    DCHECK_GE(params.embedded_worker_id, 0);
    WorkerResponseCallbackMapKey key(render_process_id,
                                     params.embedded_worker_id);
    UIThreadWorkerResponseCallbackWrapperMap::const_iterator iter =
        ui_thread_response_callback_wrappers_for_worker_.find(key);
    UIThreadWorkerResponseCallbackWrapper* callback_wrapper = nullptr;
    if (iter == ui_thread_response_callback_wrappers_for_worker_.end()) {
      callback_wrapper = new UIThreadWorkerResponseCallbackWrapper(
          AsWeakPtr(), render_process_id, params.worker_thread_id);
      ui_thread_response_callback_wrappers_for_worker_[key] =
          base::WrapUnique(callback_wrapper);
    } else {
      callback_wrapper = iter->second.get();
    }
    DispatchWithCallbackInternal(
        params, nullptr, render_process_id,
        callback_wrapper->CreateCallback(params.request_id));
  }
}

void ExtensionFunctionDispatcher::DispatchWithCallbackInternal(
    const ExtensionHostMsg_Request_Params& params,
    content::RenderFrameHost* render_frame_host,
    int render_process_id,
    const ExtensionFunction::ResponseCallback& callback) {
  // TODO(yzshen): There is some shared logic between this method and
  // DispatchOnIOThread(). It is nice to deduplicate.
  ProcessMap* process_map = ProcessMap::Get(browser_context_);
  if (!process_map)
    return;

  ExtensionRegistry* registry = ExtensionRegistry::Get(browser_context_);
  const Extension* extension =
      registry->enabled_extensions().GetByID(params.extension_id);
  if (!extension) {
    extension =
        registry->enabled_extensions().GetHostedAppByURL(params.source_url);
  }

  if (render_frame_host)
    DCHECK_EQ(render_process_id, render_frame_host->GetProcess()->GetID());

  scoped_refptr<ExtensionFunction> function(CreateExtensionFunction(
      params, extension, render_process_id, *process_map,
      ExtensionAPI::GetSharedInstance(), browser_context_, callback));
  if (!function.get())
    return;

  UIThreadExtensionFunction* function_ui =
      function->AsUIThreadExtensionFunction();
  if (!function_ui) {
    NOTREACHED();
    return;
  }
  if (params.embedded_worker_id != -1) {
    function_ui->set_is_from_service_worker(true);
  } else {
    function_ui->SetRenderFrameHost(render_frame_host);
  }
  function_ui->set_dispatcher(AsWeakPtr());
  function_ui->set_browser_context(browser_context_);
  if (extension &&
      ExtensionsBrowserClient::Get()->CanExtensionCrossIncognito(
          extension, browser_context_)) {
    function->set_include_incognito(true);
  }

  if (!CheckPermissions(function.get(), params, callback))
    return;

  if (!extension) {
    // Skip all of the UMA, quota, event page, activity logging stuff if there
    // isn't an extension, e.g. if the function call was from WebUI.
    function->RunWithValidation()->Execute();
    return;
  }

  // Fetch the ProcessManager before |this| is possibly invalidated.
  ProcessManager* process_manager = ProcessManager::Get(browser_context_);

  ExtensionSystem* extension_system = ExtensionSystem::Get(browser_context_);
  QuotaService* quota = extension_system->quota_service();
  std::string violation_error = quota->Assess(extension->id(),
                                              function.get(),
                                              &params.arguments,
                                              base::TimeTicks::Now());

  if (violation_error.empty()) {
    std::unique_ptr<base::ListValue> args(params.arguments.DeepCopy());

    // See crbug.com/39178.
    ExtensionsBrowserClient::Get()->PermitExternalProtocolHandler();
    NotifyApiFunctionCalled(extension->id(), params.name, std::move(args),
                            browser_context_);
    UMA_HISTOGRAM_SPARSE_SLOWLY("Extensions.FunctionCalls",
                                function->histogram_value());
    tracked_objects::ScopedProfile scoped_profile(
        FROM_HERE_WITH_EXPLICIT_FUNCTION(function->name()),
        tracked_objects::ScopedProfile::ENABLED);
    base::ElapsedTimer timer;
    function->RunWithValidation()->Execute();
    // TODO(devlin): Once we have a baseline metric for how long functions take,
    // we can create a handful of buckets and record the function name so that
    // we can find what the fastest/slowest are.
    // Note: Many functions execute finish asynchronously, so this time is not
    // always a representation of total time taken. See also
    // Extensions.Functions.TotalExecutionTime.
    UMA_HISTOGRAM_TIMES("Extensions.Functions.SynchronousExecutionTime",
                        timer.Elapsed());
  } else {
    function->OnQuotaExceeded(violation_error);
  }

  // Note: do not access |this| after this point. We may have been deleted
  // if function->Run() ended up closing the tab that owns us.

  // Check if extension was uninstalled by management.uninstall.
  if (!registry->enabled_extensions().GetByID(params.extension_id))
    return;

  // We only adjust the keepalive count for UIThreadExtensionFunction for
  // now, largely for simplicity's sake. This is OK because currently, only
  // the webRequest API uses IOThreadExtensionFunction, and that API is not
  // compatible with lazy background pages.
  // TODO(lazyboy): API functions from extension Service Worker will incorrectly
  // change keepalive count below.
  process_manager->IncrementLazyKeepaliveCount(extension);
}

void ExtensionFunctionDispatcher::RemoveWorkerCallbacksForProcess(
    int render_process_id) {
  UIThreadWorkerResponseCallbackWrapperMap& map =
      ui_thread_response_callback_wrappers_for_worker_;
  for (UIThreadWorkerResponseCallbackWrapperMap::iterator it = map.begin();
       it != map.end();) {
    if (it->first.render_process_id == render_process_id) {
      it = map.erase(it);
      continue;
    }
    ++it;
  }
}

void ExtensionFunctionDispatcher::OnExtensionFunctionCompleted(
    const Extension* extension) {
  // TODO(lazyboy): API functions from extension Service Worker will incorrectly
  // change keepalive count below.
  if (extension) {
    ProcessManager::Get(browser_context_)
        ->DecrementLazyKeepaliveCount(extension);
  }
}

WindowController*
ExtensionFunctionDispatcher::GetExtensionWindowController() const {
  return delegate_ ? delegate_->GetExtensionWindowController() : nullptr;
}

content::WebContents*
ExtensionFunctionDispatcher::GetAssociatedWebContents() const {
  return delegate_ ? delegate_->GetAssociatedWebContents() : nullptr;
}

content::WebContents*
ExtensionFunctionDispatcher::GetVisibleWebContents() const {
  return delegate_ ? delegate_->GetVisibleWebContents() :
      GetAssociatedWebContents();
}

// static
bool ExtensionFunctionDispatcher::CheckPermissions(
    ExtensionFunction* function,
    const ExtensionHostMsg_Request_Params& params,
    const ExtensionFunction::ResponseCallback& callback) {
  if (!function->HasPermission()) {
    LOG(ERROR) << "Permission denied for " << params.name;
    SendAccessDenied(callback, function->histogram_value());
    return false;
  }
  return true;
}

// static
ExtensionFunction* ExtensionFunctionDispatcher::CreateExtensionFunction(
    const ExtensionHostMsg_Request_Params& params,
    const Extension* extension,
    int requesting_process_id,
    const ProcessMap& process_map,
    ExtensionAPI* api,
    void* profile_id,
    const ExtensionFunction::ResponseCallback& callback) {
  ExtensionFunction* function =
      ExtensionFunctionRegistry::GetInstance()->NewFunction(params.name);
  if (!function) {
    LOG(ERROR) << "Unknown Extension API - " << params.name;
    SendAccessDenied(callback, extensions::functions::UNKNOWN);
    return NULL;
  }

  function->SetArgs(&params.arguments);
  function->set_source_url(params.source_url);
  function->set_request_id(params.request_id);
  function->set_has_callback(params.has_callback);
  function->set_user_gesture(params.user_gesture);
  function->set_extension(extension);
  function->set_profile_id(profile_id);
  function->set_response_callback(callback);
  function->set_source_tab_id(params.source_tab_id);
  function->set_source_context_type(
      process_map.GetMostLikelyContextType(extension, requesting_process_id));
  function->set_source_process_id(requesting_process_id);

  return function;
}

// static
void ExtensionFunctionDispatcher::SendAccessDenied(
    const ExtensionFunction::ResponseCallback& callback,
    functions::HistogramValue histogram_value) {
  base::ListValue empty_list;
  callback.Run(ExtensionFunction::FAILED, empty_list,
               "Access to extension API denied.", histogram_value);
}

}  // namespace extensions