Update from https://crrev.com/305340

cc/trees/layer_tree_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_impl.h"
 
 #include <limits>
 #include <set>
 
 #include "base/debug/trace_event.h"
@@ skipping 203 matching lines @@
   target_tree->top_controls_delta_ =
       target_tree->top_controls_delta_ -
           target_tree->sent_top_controls_delta_;
   target_tree->sent_top_controls_delta_ = 0.f;
 
   target_tree->SetPageScaleValues(
       page_scale_factor(), min_page_scale_factor(), max_page_scale_factor(),
       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 {
     target_tree->ClearViewportLayers();
   }
 
   target_tree->RegisterSelection(selection_start_, selection_end_);
 
   // This should match the property synchronization in
   // LayerTreeHost::finishCommitOnImplThread().
@@ skipping 178 matching lines @@
 void LayerTreeImpl::ApplyScrollDeltasSinceBeginMainFrame() {
   DCHECK(IsPendingTree());
   if (!root_layer())
     return;
 
   LayerTreeHostCommon::CallFunctionForSubtree(
       root_layer(), base::Bind(&ApplyScrollDeltasSinceBeginMainFrameTo));
 }
 
 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_);
 
   inner_viewport_scroll_layer_ =
       LayerById(inner_viewport_scroll_layer_id);
   DCHECK(inner_viewport_scroll_layer_);
 
   outer_viewport_scroll_layer_ =
       LayerById(outer_viewport_scroll_layer_id);
   DCHECK(outer_viewport_scroll_layer_ ||
@@ skipping 1032 matching lines @@
 }
 
 bool LayerTreeImpl::SmoothnessTakesPriority() const {
   return layer_tree_host_impl_->GetTreePriority() == SMOOTHNESS_TAKES_PRIORITY;
 }
 
 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