Making BeginFrameArgs work with TRACE_EVENT system.

cc/output/begin_frame_args.cc

Index: cc/output/begin_frame_args.cc
diff --git a/cc/output/begin_frame_args.cc b/cc/output/begin_frame_args.cc
index 92901afb1f3d897b37ca374297a8e5bc25463cbc..f74c061fda0500c6a1ae6d911b0bf5d63f12599a 100644
--- a/cc/output/begin_frame_args.cc
+++ b/cc/output/begin_frame_args.cc
@@ -2,6 +2,9 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include <string>
+
+#include "base/json/json_writer.h"
 #include "cc/output/begin_frame_args.h"
 #include "ui/gfx/frame_time.h"
 
@@ -27,6 +30,58 @@ BeginFrameArgs BeginFrameArgs::Create(base::TimeTicks frame_time,
   return BeginFrameArgs(frame_time, deadline, interval);
 }
 
+scoped_ptr<base::Value> BeginFrameArgs::AsValue() const {
+  scoped_ptr<base::DictionaryValue> state(new base::DictionaryValue);
+  state->SetString("type", "BeginFrameArgs");
+  state->SetDouble("frame_time_us", frame_time.ToInternalValue());
+  state->SetDouble("deadline_us", deadline.ToInternalValue());
+  state->SetDouble("interval_us", interval.InMicroseconds());
+  return state.PassAs<base::Value>();
+}
+
+namespace {
+
+// TODO(mithro): This class should be part of base/debug/trace code.
+class TracedValue : public base::debug::ConvertableToTraceFormat {
+ public:
+  static scoped_refptr<base::debug::ConvertableToTraceFormat> FromValue(
+      scoped_ptr<base::Value> value);
+
+  virtual void AppendAsTraceFormat(std::string* out) const OVERRIDE;
+
+ private:
+  explicit TracedValue(base::Value* value);
+  virtual ~TracedValue();
+
+  scoped_ptr<base::Value> value_;
+
+  DISALLOW_COPY_AND_ASSIGN(TracedValue);
+};
+
+scoped_refptr<base::debug::ConvertableToTraceFormat> TracedValue::FromValue(
+    scoped_ptr<base::Value> value) {
+  return scoped_refptr<base::debug::ConvertableToTraceFormat>(
+      new TracedValue(value.release()));
+}
+
+TracedValue::~TracedValue() {
+}
+
+void TracedValue::AppendAsTraceFormat(std::string* out) const {
+  std::string tmp;
+  base::JSONWriter::Write(value_.get(), &tmp);
+  *out += tmp;
+}
+
+TracedValue::TracedValue(base::Value* value) : value_(value) {
+}
+}  // namespace
+
+scoped_refptr<base::debug::ConvertableToTraceFormat> BeginFrameArgs::AsTrace()
+    const {
+  return TracedValue::FromValue(AsValue());
+}
+
 BeginFrameArgs BeginFrameArgs::CreateForSynchronousCompositor() {
   // For WebView/SynchronousCompositor, we always want to draw immediately,
   // so we set the deadline to 0 and guess that the interval is 16 milliseconds.