cc: Scroll on main when possible incorrect hit testing hits scrollbar.

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 2653 matching lines @@
   gfx::Point viewport_point(scroll_state->start_position_x(),
                             scroll_state->start_position_y());
 
   gfx::PointF device_viewport_point = gfx::ScalePoint(
       gfx::PointF(viewport_point), active_tree_->device_scale_factor());
   LayerImpl* layer_impl =
       active_tree_->FindLayerThatIsHitByPoint(device_viewport_point);
 
   if (layer_impl) {
     LayerImpl* scroll_layer_impl =
-        active_tree_->FindFirstScrollingLayerThatIsHitByPoint(
+        active_tree_->FindFirstScrollingLayerOrScrollbarLayerThatIsHitByPoint(
             device_viewport_point);
     if (scroll_layer_impl &&
         !HasScrollAncestor(layer_impl, scroll_layer_impl)) {
       scroll_status.thread = SCROLL_UNKNOWN;
       scroll_status.main_thread_scrolling_reasons =
           MainThreadScrollingReason::kFailedHitTest;
       return scroll_status;
     }
   }
 
@@ skipping 1291 matching lines @@
   return task_runner_provider_->HasImplThread();
 }
 
 bool LayerTreeHostImpl::CommitToActiveTree() const {
   // In single threaded mode we skip the pending tree and commit directly to the
   // active tree.
   return !task_runner_provider_->HasImplThread();
 }
 
 }  // namespace cc