Add builders for tracing event's structural arguments

cc/resources/image_raster_worker_pool.cc

Index: cc/resources/image_raster_worker_pool.cc
diff --git a/cc/resources/image_raster_worker_pool.cc b/cc/resources/image_raster_worker_pool.cc
index 79cfe37e9468028550e4158ef42ff0dc41964d6b..8ac59d306ed332b48fee6649a68673395d2dbcaa 100644
--- a/cc/resources/image_raster_worker_pool.cc
+++ b/cc/resources/image_raster_worker_pool.cc
@@ -5,6 +5,7 @@
 #include "cc/resources/image_raster_worker_pool.h"
 
 #include "base/debug/trace_event.h"
+#include "base/debug/trace_event_argument.h"
 #include "cc/debug/traced_value.h"
 #include "cc/resources/resource.h"
 
@@ -118,12 +119,7 @@ void ImageRasterWorkerPool::ScheduleTasks(RasterTaskQueue* queue) {
       new_raster_required_for_activation_finished_task;
 
   TRACE_EVENT_ASYNC_STEP_INTO1(
-      "cc",
-      "ScheduledTasks",
-      this,
-      "rasterizing",
-      "state",
-      TracedValue::FromValue(StateAsValue().release()));
+      "cc", "ScheduledTasks", this, "rasterizing", "state", StateAsValue());
 }
 
 void ImageRasterWorkerPool::CheckForCompletedTasks() {
@@ -174,21 +170,18 @@ void ImageRasterWorkerPool::OnRasterRequiredForActivationFinished() {
   DCHECK(raster_tasks_required_for_activation_pending_);
   raster_tasks_required_for_activation_pending_ = false;
   TRACE_EVENT_ASYNC_STEP_INTO1(
-      "cc",
-      "ScheduledTasks",
-      this,
-      "rasterizing",
-      "state",
-      TracedValue::FromValue(StateAsValue().release()));
+      "cc", "ScheduledTasks", this, "rasterizing", "state", StateAsValue());
   client_->DidFinishRunningTasksRequiredForActivation();
 }
 
-scoped_ptr<base::Value> ImageRasterWorkerPool::StateAsValue() const {
-  scoped_ptr<base::DictionaryValue> state(new base::DictionaryValue);
+scoped_refptr<base::debug::ConvertableToTraceFormat>
+ImageRasterWorkerPool::StateAsValue() const {
+  scoped_refptr<base::debug::TracedValue> state =
+      new base::debug::TracedValue();
 
   state->SetBoolean("tasks_required_for_activation_pending",
                     raster_tasks_required_for_activation_pending_);
-  return state.PassAs<base::Value>();
+  return state;
 }
 
 }  // namespace cc