Add builders for tracing event's structural arguments

cc/trees/layer_tree_impl.cc

Index: cc/trees/layer_tree_impl.cc
diff --git a/cc/trees/layer_tree_impl.cc b/cc/trees/layer_tree_impl.cc
index 4b21b145123e06c2d5f308353f9a3ce6741d463b..c054b783c196408aebbca92e74457579762d2b57 100644
--- a/cc/trees/layer_tree_impl.cc
+++ b/cc/trees/layer_tree_impl.cc
@@ -8,6 +8,7 @@
 #include <set>
 
 #include "base/debug/trace_event.h"
+#include "base/debug/trace_event_argument.h"
 #include "cc/animation/keyframed_animation_curve.h"
 #include "cc/animation/scrollbar_animation_controller.h"
 #include "cc/animation/scrollbar_animation_controller_linear_fade.h"
@@ -820,26 +821,23 @@ AnimationRegistrar* LayerTreeImpl::animationRegistrar() const {
   return layer_tree_host_impl_->animation_registrar();
 }
 
-scoped_ptr<base::Value> LayerTreeImpl::AsValue() const {
-  scoped_ptr<base::DictionaryValue> state(new base::DictionaryValue());
-  TracedValue::MakeDictIntoImplicitSnapshot(
-      state.get(), "cc::LayerTreeImpl", this);
+void LayerTreeImpl::AsValueInto(base::debug::TracedValue* state) const {
+  TracedValue::MakeDictIntoImplicitSnapshot(state, "cc::LayerTreeImpl", this);
 
-  state->Set("root_layer", root_layer_->AsValue().release());
+  state->BeginDictionary("root_layer");
+  root_layer_->AsValueInto(state);
+  state->EndDictionary();
 
-  scoped_ptr<base::ListValue> render_surface_layer_list(new base::ListValue());
+  state->BeginArray("render_surface_layer_list");
   typedef LayerIterator<LayerImpl> LayerIteratorType;
   LayerIteratorType end = LayerIteratorType::End(&render_surface_layer_list_);
   for (LayerIteratorType it = LayerIteratorType::Begin(
            &render_surface_layer_list_); it != end; ++it) {
     if (!it.represents_itself())
       continue;
-    render_surface_layer_list->Append(TracedValue::CreateIDRef(*it).release());
+    TracedValue::AppendIDRef(*it, state);
   }
-
-  state->Set("render_surface_layer_list",
-             render_surface_layer_list.release());
-  return state.PassAs<base::Value>();
+  state->EndArray();
 }
 
 void LayerTreeImpl::SetRootLayerScrollOffsetDelegate(