Update from https://crrev.com/305340

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 c005a1821614499203bbcdb488a40e4e595698c2..ad355fa977b0cc0168c28f8c21defcba7784263c 100644
--- a/cc/trees/layer_tree_impl.cc
+++ b/cc/trees/layer_tree_impl.cc
@@ -221,12 +221,14 @@ void LayerTreeImpl::PushPropertiesTo(LayerTreeImpl* target_tree) {
       target_tree->page_scale_delta() / target_tree->sent_page_scale_delta());
   target_tree->set_sent_page_scale_delta(1);
 
-  target_tree->page_scale_animation_ = page_scale_animation_.Pass();
+  target_tree->pending_page_scale_animation_ =
+      pending_page_scale_animation_.Pass();
 
   if (page_scale_layer_ && inner_viewport_scroll_layer_) {
     target_tree->SetViewportLayersFromIds(
-        page_scale_layer_->id(),
-        inner_viewport_scroll_layer_->id(),
+        overscroll_elasticity_layer_ ? overscroll_elasticity_layer_->id()
+                                     : Layer::INVALID_ID,
+        page_scale_layer_->id(), inner_viewport_scroll_layer_->id(),
         outer_viewport_scroll_layer_ ? outer_viewport_scroll_layer_->id()
                                      : Layer::INVALID_ID);
   } else {
@@ -425,9 +427,11 @@ void LayerTreeImpl::ApplyScrollDeltasSinceBeginMainFrame() {
 }
 
 void LayerTreeImpl::SetViewportLayersFromIds(
+    int overscroll_elasticity_layer_id,
     int page_scale_layer_id,
     int inner_viewport_scroll_layer_id,
     int outer_viewport_scroll_layer_id) {
+  overscroll_elasticity_layer_ = LayerById(overscroll_elasticity_layer_id);
   page_scale_layer_ = LayerById(page_scale_layer_id);
   DCHECK(page_scale_layer_);
 
@@ -1480,45 +1484,14 @@ BlockingTaskRunner* LayerTreeImpl::BlockingMainThreadTaskRunner() const {
   return proxy()->blocking_main_thread_task_runner();
 }
 
-void LayerTreeImpl::SetPageScaleAnimation(
-    const gfx::Vector2d& target_offset,
-    bool anchor_point,
-    float page_scale,
-    base::TimeDelta duration) {
-  if (!InnerViewportScrollLayer())
-    return;
-
-  gfx::ScrollOffset scroll_total = TotalScrollOffset();
-  gfx::SizeF scaled_scrollable_size = ScrollableSize();
-  gfx::SizeF viewport_size = InnerViewportContainerLayer()->bounds();
-
-  // Easing constants experimentally determined.
-  scoped_ptr<TimingFunction> timing_function =
-      CubicBezierTimingFunction::Create(.8, 0, .3, .9);
-
-  // TODO(miletus) : Pass in ScrollOffset.
-  page_scale_animation_ =
-      PageScaleAnimation::Create(ScrollOffsetToVector2dF(scroll_total),
-                                 total_page_scale_factor(),
-                                 viewport_size,
-                                 scaled_scrollable_size,
-                                 timing_function.Pass());
-
-  if (anchor_point) {
-    gfx::Vector2dF anchor(target_offset);
-    page_scale_animation_->ZoomWithAnchor(anchor,
-                                          page_scale,
-                                          duration.InSecondsF());
-  } else {
-    gfx::Vector2dF scaled_target_offset = target_offset;
-    page_scale_animation_->ZoomTo(scaled_target_offset,
-                                  page_scale,
-                                  duration.InSecondsF());
-  }
+void LayerTreeImpl::SetPendingPageScaleAnimation(
+    scoped_ptr<PendingPageScaleAnimation> pending_animation) {
+  pending_page_scale_animation_ = pending_animation.Pass();
 }
 
-scoped_ptr<PageScaleAnimation> LayerTreeImpl::TakePageScaleAnimation() {
-  return page_scale_animation_.Pass();
+scoped_ptr<PendingPageScaleAnimation>
+    LayerTreeImpl::TakePendingPageScaleAnimation() {
+  return pending_page_scale_animation_.Pass();
 }
 
 }  // namespace cc