Add flag for drawing layers to screen with Ganesh

cc/layers/layer_impl.cc

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/layers/layer_impl.h"
 
 #include "base/debug/trace_event.h"
 #include "base/stringprintf.h"
 #include "cc/animation/animation_registrar.h"
 #include "cc/animation/scrollbar_animation_controller.h"
@@ skipping 542 matching lines @@
   NoteLayerPropertyChanged();
   NoteLayerPropertyChangedForDescendants();
 }
 
 void LayerImpl::NoteLayerPropertyChangedForDescendants() {
   layer_tree_impl()->set_needs_update_draw_properties();
   for (size_t i = 0; i < children_.size(); ++i)
     children_[i]->NoteLayerPropertyChangedForSubtree();
 }
 
+bool LayerImpl::CanDrawDirectlyToBackbuffer() const {
+  return render_target() == layer_tree_impl_->root_layer() &&
+      draw_opacity() == 1.f && !draw_opacity_is_animating();
+}
+
 const char* LayerImpl::LayerTypeAsString() const {
   return "Layer";
 }
 
 void LayerImpl::ResetAllChangeTrackingForSubtree() {
   layer_property_changed_ = false;
   layer_surface_property_changed_ = false;
 
   update_rect_ = gfx::RectF();
 
@@ skipping 454 matching lines @@
     state->Set("replica_layer", replica_layer_->AsValue().release());
 }
 
 scoped_ptr<base::Value> LayerImpl::AsValue() const {
   scoped_ptr<base::DictionaryValue> state(new base::DictionaryValue());
   AsValueInto(state.get());
   return state.PassAs<base::Value>();
 }
 
 }  // namespace cc