Report LatencyInfo through trace buffer

ui/events/latency_info.cc

Index: ui/events/latency_info.cc
diff --git a/ui/events/latency_info.cc b/ui/events/latency_info.cc
index 796f442ae6d953de923edf7a131048c4ad046e4c..3ab67f9d6e1d501eb9d1699d977df33afc03d887 100644
--- a/ui/events/latency_info.cc
+++ b/ui/events/latency_info.cc
@@ -2,13 +2,114 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include "base/debug/trace_event.h"
+#include "base/json/json_writer.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/strings/stringprintf.h"
 #include "ui/events/latency_info.h"
 
 #include <algorithm>
 
+namespace {
+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_SCROLL_UPDATE_RWH_COMPONENT);
+    CASE_TYPE(INPUT_EVENT_LATENCY_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_ACKED_TOUCH_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);
+    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:
+      return true;
+    default:
+      return false;
+  }
+}
+
+bool IsBeginComponent(ui::LatencyComponentType type) {
+  if (type == ui::INPUT_EVENT_LATENCY_BEGIN_RWH_COMPONENT)
+    return true;
+  return false;
+}
+
+// This class is for converting latency info to trace buffer friendly format.
+class LatencyInfoTracedValue : public base::debug::ConvertableToTraceFormat {
+ public:
+  static scoped_ptr<ConvertableToTraceFormat> FromValue(
+      base::Value* value);
+
+  virtual ~LatencyInfoTracedValue();
+
+  virtual void AppendAsTraceFormat(std::string* out) const OVERRIDE;
+
+ private:
+  explicit LatencyInfoTracedValue(base::Value* value);
+
+  scoped_ptr<base::Value> value_;
+
+  DISALLOW_COPY_AND_ASSIGN(LatencyInfoTracedValue);
+};
+
+scoped_ptr<base::debug::ConvertableToTraceFormat>
+LatencyInfoTracedValue::FromValue(base::Value* value) {
+  LatencyInfoTracedValue* ptr = new LatencyInfoTracedValue(value);
+  scoped_ptr<LatencyInfoTracedValue> result(ptr);
+  return result.PassAs<base::debug::ConvertableToTraceFormat>();
+}
+
+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_ptr<base::debug::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", it->first.second);
+    component_info->SetDouble("time", it->second.event_time.ToInternalValue());
+    component_info->SetDouble("count", it->second.event_count);
+    record_data->Set(GetComponentName(it->first.first), component_info);
+  }
+  return LatencyInfoTracedValue::FromValue(record_data.release());
+}
+
+}  // namespace
+
 namespace ui {
 
-LatencyInfo::LatencyInfo() {
+LatencyInfo::LatencyInfo() : trace_id(-1), terminated(false) {
 }
 
 LatencyInfo::~LatencyInfo() {
@@ -43,8 +144,27 @@ void LatencyInfo::AddNewLatencyFrom(const LatencyInfo& other) {
 void LatencyInfo::AddLatencyNumber(LatencyComponentType component,
                                    int64 id,
                                    int64 component_sequence_number) {
+  if (IsBeginComponent(component)) {
+    // Should only ever add begin component once.
+    CHECK(trace_id == -1);
+    trace_id = component_sequence_number;
+    TRACE_EVENT_ASYNC_BEGIN0("benchmark",
+                             "InputLatency",
+                             TRACE_ID_DONT_MANGLE(trace_id));
+  }
+
   AddLatencyNumberWithTimestamp(component, id, component_sequence_number,
                                 base::TimeTicks::HighResNow(), 1);
+
+  if (IsTerminalComponent(component) && trace_id != -1) {
+    // Should only ever add terminal component once.
+    CHECK(!terminated);
+    terminated = true;
+    TRACE_EVENT_ASYNC_END1("benchmark",
+                           "InputLatency",
+                           TRACE_ID_DONT_MANGLE(trace_id),
+                           "data", AsTraceableData(*this));
+  }
 }
 
 void LatencyInfo::AddLatencyNumberWithTimestamp(LatencyComponentType component,