Scroll on main if impl-hit testing isn't guaranteed to be correct

cc/trees/layer_tree_host_common.h

 // 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.
 
 #ifndef CC_TREES_LAYER_TREE_HOST_COMMON_H_
 #define CC_TREES_LAYER_TREE_HOST_COMMON_H_
 
 #include <limits>
 #include <vector>
 
@@ skipping 78 matching lines @@
   typedef CalcDrawPropsInputsForTesting<Layer, RenderSurfaceLayerList>
       CalcDrawPropsMainInputsForTesting;
   static void CalculateDrawProperties(CalcDrawPropsMainInputs* inputs);
 
   typedef CalcDrawPropsInputs<LayerImpl, LayerImplList> CalcDrawPropsImplInputs;
   typedef CalcDrawPropsInputsForTesting<LayerImpl, LayerImplList>
       CalcDrawPropsImplInputsForTesting;
   static void CalculateDrawProperties(CalcDrawPropsImplInputs* inputs);
 
   // Performs hit testing for a given render_surface_layer_list.
+  static LayerImpl* FindFirstScrollingLayerThatIsHitByPoint(
+      const gfx::PointF& screen_space_point,
+      const LayerImplList& render_surface_layer_list);
+
+  // Performs hit testing for a given render_surface_layer_list.
   static LayerImpl* FindLayerThatIsHitByPoint(
       const gfx::PointF& screen_space_point,
       const LayerImplList& render_surface_layer_list);
 
   static LayerImpl* FindLayerThatIsHitByPointInTouchHandlerRegion(
       const gfx::PointF& screen_space_point,
       const LayerImplList& render_surface_layer_list);
 
   static bool LayerHasTouchEventHandlersAt(
       const gfx::PointF& screen_space_point,
@@ skipping 141 matching lines @@
           true,
           false,
           render_surface_layer_list) {
   DCHECK(root_layer);
   DCHECK(render_surface_layer_list);
 }
 
 }  // namespace cc
 
 #endif  // CC_TREES_LAYER_TREE_HOST_COMMON_H_