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

cc/trees/layer_tree_host.cc

Index: cc/trees/layer_tree_host.cc
diff --git a/cc/trees/layer_tree_host.cc b/cc/trees/layer_tree_host.cc
index d93e3d5e032e80c8cf353b672338904f832a16f2..14ea6b0b3dc9e3779fac85d39f78c44c5a503af2 100644
--- a/cc/trees/layer_tree_host.cc
+++ b/cc/trees/layer_tree_host.cc
@@ -1058,11 +1058,15 @@ void LayerTreeHost::PaintLayerContents(
       PaintMasksForRenderSurface(
           *it, queue, did_paint_content, need_more_updates);
     } else if (it.represents_itself() && it->DrawsContent()) {
-      devtools_instrumentation::ScopedLayerTreeTask
-          update_layer(devtools_instrumentation::kUpdateLayer, it->id(), id());
-      DCHECK(!it->paint_properties().bounds.IsEmpty());
-      *did_paint_content |= it->Update(queue, &occlusion_tracker);
-      *need_more_updates |= it->NeedMoreUpdates();
+      bool zero_opacity = !it->draw_opacity() &&

[enne (OOO), 2013/10/29 23:54:22]

Zero opacity is not the only reason to skip a layer or a subtree.   Can you add
a "visible" draw property that both append quads and update layers can respect? 
It would be set to true if before this patch that layer would end up in the RSLL
(i.e. would be skipped except for input) and false otherwise.

[sadrul, 2013/10/30 15:44:42]

Done (I am calling it 'skip_drawing' to be more like *ShouldBeSkipped()).

+                          !it->draw_opacity_is_animating();
+      if (!zero_opacity) {
+        devtools_instrumentation::ScopedLayerTreeTask update_layer(
+            devtools_instrumentation::kUpdateLayer, it->id(), id());
+        DCHECK(!it->paint_properties().bounds.IsEmpty());
+        *did_paint_content |= it->Update(queue, &occlusion_tracker);
+        *need_more_updates |= it->NeedMoreUpdates();
+      }
     }
 
     occlusion_tracker.LeaveLayer(it);