cc: Fix hit-testing in zero-opacity layers.

cc/layers/draw_properties.h

Index: cc/layers/draw_properties.h
diff --git a/cc/layers/draw_properties.h b/cc/layers/draw_properties.h
index 990b4c97d3012ae17464bac28975f90a0220ea27..fffb5a9b637ddc09399ac797cae9b6b85b175491 100644
--- a/cc/layers/draw_properties.h
+++ b/cc/layers/draw_properties.h
@@ -35,7 +35,8 @@ struct CC_EXPORT DrawProperties {
         index_of_first_descendants_addition(0),
         num_descendants_added(0),
         index_of_first_render_surface_layer_list_addition(0),
-        num_render_surfaces_added(0) {}
+        num_render_surfaces_added(0),
+        skip_drawing(false) {}
 
   // Transforms objects from content space to target surface space, where
   // this layer would be drawn.
@@ -121,6 +122,12 @@ struct CC_EXPORT DrawProperties {
   size_t num_descendants_added;
   size_t index_of_first_render_surface_layer_list_addition;
   size_t num_render_surfaces_added;
+
+  // If the layer is part of a [sub]tree that has a touch/wheel event handler,
+  // then the layer is not skipped during CalculateDrawPropertiesInternal, even
+  // if it does not actually have anything to draw (e.g. zero opacity, or empty
+  // content). This flag is used to keep track of such layers.
+  bool skip_drawing;
 };
 
 }  // namespace cc