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..d21dc0b79d8de35f26f4144523573f9a1fe05d5e 100644
--- a/cc/output/begin_frame_args.cc
+++ b/cc/output/begin_frame_args.cc
@@ -2,6 +2,7 @@
 // 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 "cc/output/begin_frame_args.h"
 #include "ui/gfx/frame_time.h"
 
@@ -27,6 +28,15 @@ 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>();
+}
+
 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.