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 181d900f267c33819a12f1cbf64b870176ae9184..40d6172f8a6e2249349adfc5a3acbe6643a08c4b 100644
--- a/cc/layers/draw_properties.h
+++ b/cc/layers/draw_properties.h
@@ -30,7 +30,8 @@ struct CC_EXPORT DrawProperties {
         num_unclipped_descendants(0),
         descendants_can_clip_selves(false),
         can_draw_directly_to_backbuffer(false),
-        layer_or_descendant_has_copy_request(false) {}
+        layer_or_descendant_has_copy_request(false),
+        layer_or_descendant_has_event_handler(false) {}
 
   // Transforms objects from content space to target surface space, where
   // this layer would be drawn.
@@ -102,6 +103,10 @@ struct CC_EXPORT DrawProperties {
   // If true, the layer or some layer in its sub-tree has a CopyOutputRequest
   // present on it.
   bool layer_or_descendant_has_copy_request;
+
+  // If true, the layer or some layer in its sub-tree has mousewheel or touch
+  // event handlers,
+  bool layer_or_descendant_has_event_handler;
 };
 
 }  // namespace cc