ui/events/latency_info.cc - chromium/src - Git at Google

 // Copyright 2013 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 "base/json/json_writer.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/strings/stringprintf.h"
 #include "base/trace_event/trace_event.h"
 #include "ui/events/latency_info.h"

 #include <algorithm>

 namespace {

 const size_t kMaxLatencyInfoNumber = 100;

 const char* GetComponentName(ui::LatencyComponentType type) {
 #define CASE_TYPE(t) case ui::t:  return #t
   switch (type) {
     CASE_TYPE(INPUT_EVENT_LATENCY_BEGIN_RWH_COMPONENT);
     CASE_TYPE(INPUT_EVENT_LATENCY_BEGIN_PLUGIN_COMPONENT);
     CASE_TYPE(INPUT_EVENT_LATENCY_BEGIN_SCROLL_UPDATE_MAIN_COMPONENT);
     CASE_TYPE(INPUT_EVENT_LATENCY_SCROLL_UPDATE_ORIGINAL_COMPONENT);
     CASE_TYPE(INPUT_EVENT_LATENCY_FIRST_SCROLL_UPDATE_ORIGINAL_COMPONENT);
     CASE_TYPE(INPUT_EVENT_LATENCY_ORIGINAL_COMPONENT);
     CASE_TYPE(INPUT_EVENT_LATENCY_UI_COMPONENT);
     CASE_TYPE(INPUT_EVENT_LATENCY_RENDERING_SCHEDULED_COMPONENT);
     CASE_TYPE(INPUT_EVENT_LATENCY_FORWARD_SCROLL_UPDATE_TO_MAIN_COMPONENT);
     CASE_TYPE(INPUT_EVENT_LATENCY_ACK_RWH_COMPONENT);
     CASE_TYPE(WINDOW_SNAPSHOT_FRAME_NUMBER_COMPONENT);
     CASE_TYPE(WINDOW_OLD_SNAPSHOT_FRAME_NUMBER_COMPONENT);
     CASE_TYPE(INPUT_EVENT_BROWSER_RECEIVED_RENDERER_SWAP_COMPONENT);
     CASE_TYPE(INPUT_EVENT_GPU_SWAP_BUFFER_COMPONENT);
     CASE_TYPE(INPUT_EVENT_LATENCY_TERMINATED_MOUSE_COMPONENT);
     CASE_TYPE(INPUT_EVENT_LATENCY_TERMINATED_TOUCH_COMPONENT);
     CASE_TYPE(INPUT_EVENT_LATENCY_TERMINATED_GESTURE_COMPONENT);
     CASE_TYPE(INPUT_EVENT_LATENCY_TERMINATED_FRAME_SWAP_COMPONENT);
     CASE_TYPE(INPUT_EVENT_LATENCY_TERMINATED_COMMIT_FAILED_COMPONENT);
     CASE_TYPE(INPUT_EVENT_LATENCY_TERMINATED_COMMIT_NO_UPDATE_COMPONENT);
     CASE_TYPE(INPUT_EVENT_LATENCY_TERMINATED_SWAP_FAILED_COMPONENT);
     CASE_TYPE(INPUT_EVENT_LATENCY_TERMINATED_PLUGIN_COMPONENT);
     default:
       DLOG(WARNING) << "Unhandled LatencyComponentType.\n";
       break;
   }
 #undef CASE_TYPE
   return "unknown";
 }

 bool IsTerminalComponent(ui::LatencyComponentType type) {
   switch (type) {
     case ui::INPUT_EVENT_LATENCY_TERMINATED_MOUSE_COMPONENT:
     case ui::INPUT_EVENT_LATENCY_TERMINATED_TOUCH_COMPONENT:
     case ui::INPUT_EVENT_LATENCY_TERMINATED_GESTURE_COMPONENT:
     case ui::INPUT_EVENT_LATENCY_TERMINATED_FRAME_SWAP_COMPONENT:
     case ui::INPUT_EVENT_LATENCY_TERMINATED_COMMIT_FAILED_COMPONENT:
     case ui::INPUT_EVENT_LATENCY_TERMINATED_COMMIT_NO_UPDATE_COMPONENT:
     case ui::INPUT_EVENT_LATENCY_TERMINATED_SWAP_FAILED_COMPONENT:
     case ui::INPUT_EVENT_LATENCY_TERMINATED_PLUGIN_COMPONENT:
       return true;
     default:
       return false;
   }
 }

 bool IsBeginComponent(ui::LatencyComponentType type) {
   return (type == ui::INPUT_EVENT_LATENCY_BEGIN_RWH_COMPONENT ||
           type == ui::INPUT_EVENT_LATENCY_BEGIN_PLUGIN_COMPONENT ||
           type == ui::INPUT_EVENT_LATENCY_BEGIN_SCROLL_UPDATE_MAIN_COMPONENT);
 }

 // This class is for converting latency info to trace buffer friendly format.
 class LatencyInfoTracedValue
     : public base::trace_event::ConvertableToTraceFormat {
  public:
   static scoped_refptr<ConvertableToTraceFormat> FromValue(
       scoped_ptr<base::Value> value);

   void AppendAsTraceFormat(std::string* out) const override;

  private:
   explicit LatencyInfoTracedValue(base::Value* value);
   ~LatencyInfoTracedValue() override;

   scoped_ptr<base::Value> value_;

   DISALLOW_COPY_AND_ASSIGN(LatencyInfoTracedValue);
 };

 scoped_refptr<base::trace_event::ConvertableToTraceFormat>
 LatencyInfoTracedValue::FromValue(scoped_ptr<base::Value> value) {
   return scoped_refptr<base::trace_event::ConvertableToTraceFormat>(
       new LatencyInfoTracedValue(value.release()));
 }

 LatencyInfoTracedValue::~LatencyInfoTracedValue() {
 }

 void LatencyInfoTracedValue::AppendAsTraceFormat(std::string* out) const {
   std::string tmp;
   base::JSONWriter::Write(value_.get(), &tmp);
   *out += tmp;
 }

 LatencyInfoTracedValue::LatencyInfoTracedValue(base::Value* value)
     : value_(value) {
 }

 // Converts latencyinfo into format that can be dumped into trace buffer.
 scoped_refptr<base::trace_event::ConvertableToTraceFormat> AsTraceableData(
     const ui::LatencyInfo& latency) {
   scoped_ptr<base::DictionaryValue> record_data(new base::DictionaryValue());
   for (ui::LatencyInfo::LatencyMap::const_iterator it =
            latency.latency_components.begin();
        it != latency.latency_components.end(); ++it) {
     base::DictionaryValue* component_info = new base::DictionaryValue();
     component_info->SetDouble("comp_id", static_cast<double>(it->first.second));
     component_info->SetDouble(
         "time", static_cast<double>(it->second.event_time.ToInternalValue()));
     component_info->SetDouble("count", it->second.event_count);
     record_data->Set(GetComponentName(it->first.first), component_info);
   }
   record_data->SetDouble("trace_id", static_cast<double>(latency.trace_id));

   scoped_ptr<base::ListValue> coordinates(new base::ListValue());
   for (size_t i = 0; i < latency.input_coordinates_size; i++) {
     scoped_ptr<base::DictionaryValue> coordinate_pair(
         new base::DictionaryValue());
     coordinate_pair->SetDouble("x", latency.input_coordinates[i].x);
     coordinate_pair->SetDouble("y", latency.input_coordinates[i].y);
     coordinates->Append(coordinate_pair.release());
   }
   record_data->Set("coordinates", coordinates.release());
   return LatencyInfoTracedValue::FromValue(record_data.Pass());
 }

 }  // namespace

 namespace ui {

 LatencyInfo::InputCoordinate::InputCoordinate() : x(0), y(0) {
 }

 LatencyInfo::InputCoordinate::InputCoordinate(float x, float y) : x(x), y(y) {
 }

 LatencyInfo::LatencyInfo()
     : input_coordinates_size(0), trace_id(-1), terminated(false) {
 }

 LatencyInfo::~LatencyInfo() {
 }

 bool LatencyInfo::Verify(const std::vector<LatencyInfo>& latency_info,
                          const char* referring_msg) {
   if (latency_info.size() > kMaxLatencyInfoNumber) {
     LOG(ERROR) << referring_msg << ", LatencyInfo vector size "
                << latency_info.size() << " is too big.";
     return false;
   }
   for (size_t i = 0; i < latency_info.size(); i++) {
     if (latency_info[i].input_coordinates_size > kMaxInputCoordinates) {
       LOG(ERROR) << referring_msg << ", coordinate vector size "
                  << latency_info[i].input_coordinates_size << " is too big.";
       return false;
     }
   }

   return true;
 }

 void LatencyInfo::CopyLatencyFrom(const LatencyInfo& other,
                                   LatencyComponentType type) {
   for (LatencyMap::const_iterator it = other.latency_components.begin();
        it != other.latency_components.end();
        ++it) {
     if (it->first.first == type) {
       AddLatencyNumberWithTimestamp(it->first.first,
                                     it->first.second,
                                     it->second.sequence_number,
                                     it->second.event_time,
                                     it->second.event_count);
     }
   }
 }

 void LatencyInfo::AddNewLatencyFrom(const LatencyInfo& other) {
     for (LatencyMap::const_iterator it = other.latency_components.begin();
          it != other.latency_components.end();
          ++it) {
       if (!FindLatency(it->first.first, it->first.second, NULL)) {
         AddLatencyNumberWithTimestamp(it->first.first,
                                       it->first.second,
                                       it->second.sequence_number,
                                       it->second.event_time,
                                       it->second.event_count);
       }
     }
 }

 void LatencyInfo::AddLatencyNumber(LatencyComponentType component,
                                    int64 id,
                                    int64 component_sequence_number) {
   AddLatencyNumberWithTimestamp(component, id, component_sequence_number,
                                 base::TimeTicks::Now(), 1);
 }

 void LatencyInfo::AddLatencyNumberWithTimestamp(LatencyComponentType component,
                                                 int64 id,
                                                 int64 component_sequence_number,
                                                 base::TimeTicks time,
                                                 uint32 event_count) {

   static const unsigned char* benchmark_enabled =
       TRACE_EVENT_API_GET_CATEGORY_GROUP_ENABLED("benchmark");

   if (IsBeginComponent(component)) {
     // Should only ever add begin component once.
     CHECK_EQ(-1, trace_id);
     trace_id = component_sequence_number;

     if (*benchmark_enabled) {
       // The timestamp for ASYNC_BEGIN trace event is used for drawing the
       // beginning of the trace event in trace viewer. For better visualization,
       // for an input event, we want to draw the beginning as when the event is
       // originally created, e.g. the timestamp of its ORIGINAL/UI_COMPONENT,
       // not when we actually issue the ASYNC_BEGIN trace event.
       LatencyComponent component;
       int64 ts = 0;
       if (FindLatency(INPUT_EVENT_LATENCY_ORIGINAL_COMPONENT,
                       0,
                       &component) ||
           FindLatency(INPUT_EVENT_LATENCY_UI_COMPONENT,
                       0,
                       &component)) {
         // The timestamp stored in ORIGINAL/UI_COMPONENT is using clock
         // CLOCK_MONOTONIC while TRACE_EVENT_ASYNC_BEGIN_WITH_TIMESTAMP0
         // expects timestamp using CLOCK_MONOTONIC or CLOCK_SYSTEM_TRACE (on
         // CrOS). So we need to adjust the diff between in CLOCK_MONOTONIC and
         // CLOCK_SYSTEM_TRACE. Note that the diff is drifting overtime so we
         // can't use a static value.
         int64 diff = base::TimeTicks::Now().ToInternalValue() -
             base::TimeTicks::NowFromSystemTraceTime().ToInternalValue();
         ts = component.event_time.ToInternalValue() - diff;
       } else {
         ts = base::TimeTicks::NowFromSystemTraceTime().ToInternalValue();
       }
       TRACE_EVENT_ASYNC_BEGIN_WITH_TIMESTAMP0(
           "benchmark",
           "InputLatency",
           TRACE_ID_DONT_MANGLE(trace_id),
           ts);
     }

     TRACE_EVENT_FLOW_BEGIN0(
         "input,benchmark", "LatencyInfo.Flow", TRACE_ID_DONT_MANGLE(trace_id));
   }

   LatencyMap::key_type key = std::make_pair(component, id);
   LatencyMap::iterator it = latency_components.find(key);
   if (it == latency_components.end()) {
     LatencyComponent info = {component_sequence_number, time, event_count};
     latency_components[key] = info;
   } else {
     it->second.sequence_number = std::max(component_sequence_number,
                                           it->second.sequence_number);
     uint32 new_count = event_count + it->second.event_count;
     if (event_count > 0 && new_count != 0) {
       // Do a weighted average, so that the new event_time is the average of
       // the times of events currently in this structure with the time passed
       // into this method.
       it->second.event_time += (time - it->second.event_time) * event_count /
           new_count;
       it->second.event_count = new_count;
     }
   }

   if (IsTerminalComponent(component) && trace_id != -1) {
     // Should only ever add terminal component once.
     CHECK(!terminated);
     terminated = true;

     if (*benchmark_enabled) {
       TRACE_EVENT_ASYNC_END1("benchmark",
                              "InputLatency",
                              TRACE_ID_DONT_MANGLE(trace_id),
                              "data", AsTraceableData(*this));
     }

     TRACE_EVENT_FLOW_END0(
         "input,benchmark", "LatencyInfo.Flow", TRACE_ID_DONT_MANGLE(trace_id));
   }
 }

 bool LatencyInfo::FindLatency(LatencyComponentType type,
                               int64 id,
                               LatencyComponent* output) const {
   LatencyMap::const_iterator it = latency_components.find(
       std::make_pair(type, id));
   if (it == latency_components.end())
     return false;
   if (output)
     *output = it->second;
   return true;
 }

 void LatencyInfo::RemoveLatency(LatencyComponentType type) {
   LatencyMap::iterator it = latency_components.begin();
   while (it != latency_components.end()) {
     if (it->first.first == type) {
       LatencyMap::iterator tmp = it;
       ++it;
       latency_components.erase(tmp);
     } else {
       it++;
     }
   }
 }

 void LatencyInfo::Clear() {
   latency_components.clear();
 }

 void LatencyInfo::TraceEventType(const char* event_type) {
   TRACE_EVENT_ASYNC_STEP_INTO0("benchmark",
                                "InputLatency",
                                TRACE_ID_DONT_MANGLE(trace_id),
                                event_type);
 }

 }  // namespace ui
	// Copyright 2013 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 "base/json/json_writer.h"
	#include "base/memory/scoped_ptr.h"
	#include "base/strings/stringprintf.h"
	#include "base/trace_event/trace_event.h"
	#include "ui/events/latency_info.h"

	#include <algorithm>

	namespace {

	const size_t kMaxLatencyInfoNumber = 100;

	const char* GetComponentName(ui::LatencyComponentType type) {
	#define CASE_TYPE(t) case ui::t: return #t
	switch (type) {
	CASE_TYPE(INPUT_EVENT_LATENCY_BEGIN_RWH_COMPONENT);
	CASE_TYPE(INPUT_EVENT_LATENCY_BEGIN_PLUGIN_COMPONENT);
	CASE_TYPE(INPUT_EVENT_LATENCY_BEGIN_SCROLL_UPDATE_MAIN_COMPONENT);
	CASE_TYPE(INPUT_EVENT_LATENCY_SCROLL_UPDATE_ORIGINAL_COMPONENT);
	CASE_TYPE(INPUT_EVENT_LATENCY_FIRST_SCROLL_UPDATE_ORIGINAL_COMPONENT);
	CASE_TYPE(INPUT_EVENT_LATENCY_ORIGINAL_COMPONENT);
	CASE_TYPE(INPUT_EVENT_LATENCY_UI_COMPONENT);
	CASE_TYPE(INPUT_EVENT_LATENCY_RENDERING_SCHEDULED_COMPONENT);
	CASE_TYPE(INPUT_EVENT_LATENCY_FORWARD_SCROLL_UPDATE_TO_MAIN_COMPONENT);
	CASE_TYPE(INPUT_EVENT_LATENCY_ACK_RWH_COMPONENT);
	CASE_TYPE(WINDOW_SNAPSHOT_FRAME_NUMBER_COMPONENT);
	CASE_TYPE(WINDOW_OLD_SNAPSHOT_FRAME_NUMBER_COMPONENT);
	CASE_TYPE(INPUT_EVENT_BROWSER_RECEIVED_RENDERER_SWAP_COMPONENT);
	CASE_TYPE(INPUT_EVENT_GPU_SWAP_BUFFER_COMPONENT);
	CASE_TYPE(INPUT_EVENT_LATENCY_TERMINATED_MOUSE_COMPONENT);
	CASE_TYPE(INPUT_EVENT_LATENCY_TERMINATED_TOUCH_COMPONENT);
	CASE_TYPE(INPUT_EVENT_LATENCY_TERMINATED_GESTURE_COMPONENT);
	CASE_TYPE(INPUT_EVENT_LATENCY_TERMINATED_FRAME_SWAP_COMPONENT);
	CASE_TYPE(INPUT_EVENT_LATENCY_TERMINATED_COMMIT_FAILED_COMPONENT);
	CASE_TYPE(INPUT_EVENT_LATENCY_TERMINATED_COMMIT_NO_UPDATE_COMPONENT);
	CASE_TYPE(INPUT_EVENT_LATENCY_TERMINATED_SWAP_FAILED_COMPONENT);
	CASE_TYPE(INPUT_EVENT_LATENCY_TERMINATED_PLUGIN_COMPONENT);
	default:
	DLOG(WARNING) << "Unhandled LatencyComponentType.\n";
	break;
	}
	#undef CASE_TYPE
	return "unknown";
	}

	bool IsTerminalComponent(ui::LatencyComponentType type) {
	switch (type) {
	case ui::INPUT_EVENT_LATENCY_TERMINATED_MOUSE_COMPONENT:
	case ui::INPUT_EVENT_LATENCY_TERMINATED_TOUCH_COMPONENT:
	case ui::INPUT_EVENT_LATENCY_TERMINATED_GESTURE_COMPONENT:
	case ui::INPUT_EVENT_LATENCY_TERMINATED_FRAME_SWAP_COMPONENT:
	case ui::INPUT_EVENT_LATENCY_TERMINATED_COMMIT_FAILED_COMPONENT:
	case ui::INPUT_EVENT_LATENCY_TERMINATED_COMMIT_NO_UPDATE_COMPONENT:
	case ui::INPUT_EVENT_LATENCY_TERMINATED_SWAP_FAILED_COMPONENT:
	case ui::INPUT_EVENT_LATENCY_TERMINATED_PLUGIN_COMPONENT:
	return true;
	default:
	return false;
	}
	}

	bool IsBeginComponent(ui::LatencyComponentType type) {
	return (type == ui::INPUT_EVENT_LATENCY_BEGIN_RWH_COMPONENT \|\|
	type == ui::INPUT_EVENT_LATENCY_BEGIN_PLUGIN_COMPONENT \|\|
	type == ui::INPUT_EVENT_LATENCY_BEGIN_SCROLL_UPDATE_MAIN_COMPONENT);
	}

	// This class is for converting latency info to trace buffer friendly format.
	class LatencyInfoTracedValue
	: public base::trace_event::ConvertableToTraceFormat {
	public:
	static scoped_refptr<ConvertableToTraceFormat> FromValue(
	scoped_ptr<base::Value> value);

	void AppendAsTraceFormat(std::string* out) const override;

	private:
	explicit LatencyInfoTracedValue(base::Value* value);
	~LatencyInfoTracedValue() override;

	scoped_ptr<base::Value> value_;

	DISALLOW_COPY_AND_ASSIGN(LatencyInfoTracedValue);
	};

	scoped_refptr<base::trace_event::ConvertableToTraceFormat>
	LatencyInfoTracedValue::FromValue(scoped_ptr<base::Value> value) {
	return scoped_refptr<base::trace_event::ConvertableToTraceFormat>(
	new LatencyInfoTracedValue(value.release()));
	}

	LatencyInfoTracedValue::~LatencyInfoTracedValue() {
	}

	void LatencyInfoTracedValue::AppendAsTraceFormat(std::string* out) const {
	std::string tmp;
	base::JSONWriter::Write(value_.get(), &tmp);
	*out += tmp;
	}

	LatencyInfoTracedValue::LatencyInfoTracedValue(base::Value* value)
	: value_(value) {
	}

	// Converts latencyinfo into format that can be dumped into trace buffer.
	scoped_refptr<base::trace_event::ConvertableToTraceFormat> AsTraceableData(
	const ui::LatencyInfo& latency) {
	scoped_ptr<base::DictionaryValue> record_data(new base::DictionaryValue());
	for (ui::LatencyInfo::LatencyMap::const_iterator it =
	latency.latency_components.begin();
	it != latency.latency_components.end(); ++it) {
	base::DictionaryValue* component_info = new base::DictionaryValue();
	component_info->SetDouble("comp_id", static_cast<double>(it->first.second));
	component_info->SetDouble(
	"time", static_cast<double>(it->second.event_time.ToInternalValue()));
	component_info->SetDouble("count", it->second.event_count);
	record_data->Set(GetComponentName(it->first.first), component_info);
	}
	record_data->SetDouble("trace_id", static_cast<double>(latency.trace_id));

	scoped_ptr<base::ListValue> coordinates(new base::ListValue());
	for (size_t i = 0; i < latency.input_coordinates_size; i++) {
	scoped_ptr<base::DictionaryValue> coordinate_pair(
	new base::DictionaryValue());
	coordinate_pair->SetDouble("x", latency.input_coordinates[i].x);
	coordinate_pair->SetDouble("y", latency.input_coordinates[i].y);
	coordinates->Append(coordinate_pair.release());
	}
	record_data->Set("coordinates", coordinates.release());
	return LatencyInfoTracedValue::FromValue(record_data.Pass());
	}

	} // namespace

	namespace ui {

	LatencyInfo::InputCoordinate::InputCoordinate() : x(0), y(0) {
	}

	LatencyInfo::InputCoordinate::InputCoordinate(float x, float y) : x(x), y(y) {
	}

	LatencyInfo::LatencyInfo()
	: input_coordinates_size(0), trace_id(-1), terminated(false) {
	}

	LatencyInfo::~LatencyInfo() {
	}

	bool LatencyInfo::Verify(const std::vector<LatencyInfo>& latency_info,
	const char* referring_msg) {
	if (latency_info.size() > kMaxLatencyInfoNumber) {
	LOG(ERROR) << referring_msg << ", LatencyInfo vector size "
	<< latency_info.size() << " is too big.";
	return false;
	}
	for (size_t i = 0; i < latency_info.size(); i++) {
	if (latency_info[i].input_coordinates_size > kMaxInputCoordinates) {
	LOG(ERROR) << referring_msg << ", coordinate vector size "
	<< latency_info[i].input_coordinates_size << " is too big.";
	return false;
	}
	}

	return true;
	}

	void LatencyInfo::CopyLatencyFrom(const LatencyInfo& other,
	LatencyComponentType type) {
	for (LatencyMap::const_iterator it = other.latency_components.begin();
	it != other.latency_components.end();
	++it) {
	if (it->first.first == type) {
	AddLatencyNumberWithTimestamp(it->first.first,
	it->first.second,
	it->second.sequence_number,
	it->second.event_time,
	it->second.event_count);
	}
	}
	}

	void LatencyInfo::AddNewLatencyFrom(const LatencyInfo& other) {
	for (LatencyMap::const_iterator it = other.latency_components.begin();
	it != other.latency_components.end();
	++it) {
	if (!FindLatency(it->first.first, it->first.second, NULL)) {
	AddLatencyNumberWithTimestamp(it->first.first,
	it->first.second,
	it->second.sequence_number,
	it->second.event_time,
	it->second.event_count);
	}
	}
	}

	void LatencyInfo::AddLatencyNumber(LatencyComponentType component,
	int64 id,
	int64 component_sequence_number) {
	AddLatencyNumberWithTimestamp(component, id, component_sequence_number,
	base::TimeTicks::Now(), 1);
	}

	void LatencyInfo::AddLatencyNumberWithTimestamp(LatencyComponentType component,
	int64 id,
	int64 component_sequence_number,
	base::TimeTicks time,
	uint32 event_count) {

	static const unsigned char* benchmark_enabled =
	TRACE_EVENT_API_GET_CATEGORY_GROUP_ENABLED("benchmark");

	if (IsBeginComponent(component)) {
	// Should only ever add begin component once.
	CHECK_EQ(-1, trace_id);
	trace_id = component_sequence_number;

	if (*benchmark_enabled) {
	// The timestamp for ASYNC_BEGIN trace event is used for drawing the
	// beginning of the trace event in trace viewer. For better visualization,
	// for an input event, we want to draw the beginning as when the event is
	// originally created, e.g. the timestamp of its ORIGINAL/UI_COMPONENT,
	// not when we actually issue the ASYNC_BEGIN trace event.
	LatencyComponent component;
	int64 ts = 0;
	if (FindLatency(INPUT_EVENT_LATENCY_ORIGINAL_COMPONENT,
	0,
	&component) \|\|
	FindLatency(INPUT_EVENT_LATENCY_UI_COMPONENT,
	0,
	&component)) {
	// The timestamp stored in ORIGINAL/UI_COMPONENT is using clock
	// CLOCK_MONOTONIC while TRACE_EVENT_ASYNC_BEGIN_WITH_TIMESTAMP0
	// expects timestamp using CLOCK_MONOTONIC or CLOCK_SYSTEM_TRACE (on
	// CrOS). So we need to adjust the diff between in CLOCK_MONOTONIC and
	// CLOCK_SYSTEM_TRACE. Note that the diff is drifting overtime so we
	// can't use a static value.
	int64 diff = base::TimeTicks::Now().ToInternalValue() -
	base::TimeTicks::NowFromSystemTraceTime().ToInternalValue();
	ts = component.event_time.ToInternalValue() - diff;
	} else {
	ts = base::TimeTicks::NowFromSystemTraceTime().ToInternalValue();
	}
	TRACE_EVENT_ASYNC_BEGIN_WITH_TIMESTAMP0(
	"benchmark",
	"InputLatency",
	TRACE_ID_DONT_MANGLE(trace_id),
	ts);
	}

	TRACE_EVENT_FLOW_BEGIN0(
	"input,benchmark", "LatencyInfo.Flow", TRACE_ID_DONT_MANGLE(trace_id));
	}

	LatencyMap::key_type key = std::make_pair(component, id);
	LatencyMap::iterator it = latency_components.find(key);
	if (it == latency_components.end()) {
	LatencyComponent info = {component_sequence_number, time, event_count};
	latency_components[key] = info;
	} else {
	it->second.sequence_number = std::max(component_sequence_number,
	it->second.sequence_number);
	uint32 new_count = event_count + it->second.event_count;
	if (event_count > 0 && new_count != 0) {
	// Do a weighted average, so that the new event_time is the average of
	// the times of events currently in this structure with the time passed
	// into this method.
	it->second.event_time += (time - it->second.event_time) * event_count /
	new_count;
	it->second.event_count = new_count;
	}
	}

	if (IsTerminalComponent(component) && trace_id != -1) {
	// Should only ever add terminal component once.
	CHECK(!terminated);
	terminated = true;

	if (*benchmark_enabled) {
	TRACE_EVENT_ASYNC_END1("benchmark",
	"InputLatency",
	TRACE_ID_DONT_MANGLE(trace_id),
	"data", AsTraceableData(*this));
	}

	TRACE_EVENT_FLOW_END0(
	"input,benchmark", "LatencyInfo.Flow", TRACE_ID_DONT_MANGLE(trace_id));
	}
	}

	bool LatencyInfo::FindLatency(LatencyComponentType type,
	int64 id,
	LatencyComponent* output) const {
	LatencyMap::const_iterator it = latency_components.find(
	std::make_pair(type, id));
	if (it == latency_components.end())
	return false;
	if (output)
	*output = it->second;
	return true;
	}

	void LatencyInfo::RemoveLatency(LatencyComponentType type) {
	LatencyMap::iterator it = latency_components.begin();
	while (it != latency_components.end()) {
	if (it->first.first == type) {
	LatencyMap::iterator tmp = it;
	++it;
	latency_components.erase(tmp);
	} else {
	it++;
	}
	}
	}

	void LatencyInfo::Clear() {
	latency_components.clear();
	}

	void LatencyInfo::TraceEventType(const char* event_type) {
	TRACE_EVENT_ASYNC_STEP_INTO0("benchmark",
	"InputLatency",
	TRACE_ID_DONT_MANGLE(trace_id),
	event_type);
	}

	} // namespace ui