cc: Make scheduling be driven by vsync for android webview.

cc/trees/layer_tree_host_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/trees/layer_tree_host_impl.h"
 
 #include <algorithm>
 #include <limits>
 #include <map>
 
@@ skipping 1417 matching lines @@
     resource_pool_->ReduceResourceUsage();
   }
   // If we're not visible, we likely released resources, so we want to
   // aggressively flush here to make sure those DeleteTextures make it to the
   // GPU process to free up the memory.
   if (output_surface_->context_provider() && !visible_) {
     output_surface_->context_provider()->ContextGL()->ShallowFlushCHROMIUM();
   }
 }
 
+void LayerTreeHostImpl::OnDraw() {
+  client_->OnDrawForOutputSurface();
+}
+
 void LayerTreeHostImpl::OnCanDrawStateChangedForTree() {
   client_->OnCanDrawStateChanged(CanDraw());
 }
 
 CompositorFrameMetadata LayerTreeHostImpl::MakeCompositorFrameMetadata() const {
   CompositorFrameMetadata metadata;
   metadata.device_scale_factor = device_scale_factor_;
   metadata.page_scale_factor = active_tree_->current_page_scale_factor();
   metadata.scrollable_viewport_size = active_tree_->ScrollableViewportSize();
   metadata.root_layer_size = active_tree_->ScrollableSize();
@@ skipping 1968 matching lines @@
   new_target.SetToMin(layer_impl->MaxScrollOffset());
 
   curve->UpdateTarget(
       animation->TrimTimeToCurrentIteration(CurrentBeginFrameArgs().frame_time)
           .InSecondsF(),
       new_target);
 
   return true;
 }
 }  // namespace cc