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

cc/trees/layer_tree_host_common.h

Index: cc/trees/layer_tree_host_common.h
diff --git a/cc/trees/layer_tree_host_common.h b/cc/trees/layer_tree_host_common.h
index 29a3c66dc69083edc1d79e6b71225dc68d0ef4f1..20b2163da11f1845d3f6a0a968a26e918d1d9a0a 100644
--- a/cc/trees/layer_tree_host_common.h
+++ b/cc/trees/layer_tree_host_common.h
@@ -96,6 +96,11 @@ class CC_EXPORT LayerTreeHostCommon {
   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);