Convert scroll offsets to use SyncedProperty.

cc/layers/layer.cc

Index: cc/layers/layer.cc
diff --git a/cc/layers/layer.cc b/cc/layers/layer.cc
index fb72c73b9c483b0b289a429e75e4095e3b71797d..f50235cb8e58d446ffa84f0a70ea96a8a882c003 100644
--- a/cc/layers/layer.cc
+++ b/cc/layers/layer.cc
@@ -965,17 +965,7 @@ void Layer::PushPropertiesTo(LayerImpl* layer) {
     layer->SetClipChildren(nullptr);
   }
 
-  // Adjust the scroll delta to be just the scrolls that have happened since
-  // the BeginMainFrame was sent.  This happens for impl-side painting
-  // in LayerImpl::ApplyScrollDeltasSinceBeginMainFrame in a separate tree walk.
-  if (layer->layer_tree_impl()->settings().impl_side_painting) {
-    layer->SetScrollOffset(scroll_offset_);
-  } else {
-    layer->SetScrollOffsetAndDelta(
-        scroll_offset_,
-        layer->ScrollDelta() - layer->sent_scroll_delta());
-    layer->SetSentScrollDelta(gfx::Vector2dF());
-  }
+  layer->PushScrollOffsetFromMainThread(scroll_offset_);
 
   // Wrap the copy_requests_ in a PostTask to the main thread.
   ScopedPtrVector<CopyOutputRequest> main_thread_copy_requests;
@@ -1018,7 +1008,8 @@ void Layer::PushPropertiesTo(LayerImpl* layer) {
 }
 
 scoped_ptr<LayerImpl> Layer::CreateLayerImpl(LayerTreeImpl* tree_impl) {
-  return LayerImpl::Create(tree_impl, layer_id_);
+  return LayerImpl::Create(tree_impl, layer_id_,
+                           new LayerImpl::SyncedScrollOffset);
 }
 
 bool Layer::DrawsContent() const {
@@ -1111,8 +1102,8 @@ void Layer::ClearRenderSurfaceLayerList() {
     render_surface_->ClearLayerLists();
 }
 
-gfx::ScrollOffset Layer::ScrollOffsetForAnimation() const {
-  return TotalScrollOffset();
+gfx::ScrollOffset Layer::ScrollOffsetForAnimation() {
+  return CurrentScrollOffset();
 }
 
 // On<Property>Animated is called due to an ongoing accelerated animation.