Experimental fix for scroll animation update bug. [DO NOT COMMIT THIS CHANGE]

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 <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 2941 matching lines @@
 
     gfx::Vector2dF delta = scroll_delta;
     if (!scroll_node->user_scrollable_horizontal)
       delta.set_x(0);
     if (!scroll_node->user_scrollable_vertical)
       delta.set_y(0);
 
     if (ScrollAnimationUpdateTarget(scroll_node, delta, delayed_by)) {
       scroll_status.thread = SCROLL_ON_IMPL_THREAD;
     } else {
-      scroll_status.thread = SCROLL_IGNORED;
-      scroll_status.main_thread_scrolling_reasons =
-          MainThreadScrollingReason::kNotScrollable;
+      if (ScrollAnimationCreate(scroll_node, scroll_delta, delayed_by)) {
+        scroll_animating_latched_node_id_ = scroll_node->id;
+        scroll_status.thread = SCROLL_ON_IMPL_THREAD;
+      } else {
+        scroll_status.thread = SCROLL_IGNORED;
+        scroll_status.main_thread_scrolling_reasons =
+            MainThreadScrollingReason::kNotScrollable;
+      }
     }
     return scroll_status;
   }
 
   ScrollStateData scroll_state_data;
   scroll_state_data.position_x = viewport_point.x();
   scroll_state_data.position_y = viewport_point.y();
   ScrollState scroll_state(scroll_state_data);
 
   // ScrollAnimated is used for animated wheel scrolls. We find the first layer
@@ skipping 1321 matching lines @@
 }
 
 void LayerTreeHostImpl::UpdateScrollSourceInfo(bool is_wheel_scroll) {
   if (is_wheel_scroll)
     has_scrolled_by_wheel_ = true;
   else
     has_scrolled_by_touch_ = true;
 }
 
 }  // namespace cc