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 a29123c8e394b95d008e0c9bb927446ac882f3ab..ea3ab2364990e2a3778c2660a06a2a1d5390e900 100644
--- a/cc/layers/layer.cc
+++ b/cc/layers/layer.cc
@@ -978,21 +978,10 @@ 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 {
-    if (layer_animation_controller_
-            ->scroll_offset_animation_was_interrupted()) {
-      layer->SetScrollOffsetAndDelta(scroll_offset_, gfx::Vector2dF());
-    } else {
-      layer->SetScrollOffsetAndDelta(
-          scroll_offset_, layer->ScrollDelta() - layer->sent_scroll_delta());
-    }
-    layer->SetSentScrollDelta(gfx::Vector2dF());
-  }
+  layer->PushScrollOffsetFromMainThread(scroll_offset_);
+  if (layer_animation_controller_->scroll_offset_animation_was_interrupted() &&
+      layer->IsActive())
+    layer->SetScrollDelta(gfx::Vector2dF());
   layer->SetMainScrollOffsetFractionalPart(MainScrollOffsetFractionalPart());
 
   // Wrap the copy_requests_ in a PostTask to the main thread.
@@ -1041,7 +1030,8 @@ 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 {
@@ -1135,7 +1125,7 @@ void Layer::ClearRenderSurfaceLayerList() {
 }
 
 gfx::ScrollOffset Layer::ScrollOffsetForAnimation() const {
-  return TotalScrollOffset();
+  return CurrentScrollOffset();
 }
 
 // On<Property>Animated is called due to an ongoing accelerated animation.