Reland: Refactor unreliable hit test code to avoid owning_layers

cc/layers/layer_impl.h

Index: cc/layers/layer_impl.h
diff --git a/cc/layers/layer_impl.h b/cc/layers/layer_impl.h
index d2b5c39f33bc9b37bb5be592f05d7294cd08f34c..396cda82c130b37c9835592645a080429af309e4 100644
--- a/cc/layers/layer_impl.h
+++ b/cc/layers/layer_impl.h
@@ -394,6 +394,10 @@ class CC_EXPORT LayerImpl {
     return is_drawn_render_surface_layer_list_member_;
   }
 
+  bool IsDrawnScrollbar() {
+    return ToScrollbarLayer() && is_drawn_render_surface_layer_list_member_;
+  }
+
   void set_may_contain_video(bool yes) { may_contain_video_ = yes; }
   bool may_contain_video() const { return may_contain_video_; }