Compositor hit-testing considers scrollable layers that scroll a drawn RSLL

cc/trees/layer_tree_impl.cc

Index: cc/trees/layer_tree_impl.cc
diff --git a/cc/trees/layer_tree_impl.cc b/cc/trees/layer_tree_impl.cc
index 62e4cd36bed352c3ce953c43235fcfb8503c51f9..6b029e46060aa980516cc80ef946a54bff0e437d 100644
--- a/cc/trees/layer_tree_impl.cc
+++ b/cc/trees/layer_tree_impl.cc
@@ -1448,15 +1448,16 @@ static void FindClosestMatchingLayer(
 static bool ScrollsAnyDrawnRenderSurfaceLayerListMember(LayerImpl* layer) {
   if (!layer->scrollable())
     return false;
-  if (layer->IsDrawnRenderSurfaceLayerListMember())
+  if (layer->draw_properties().layer_or_descendant_is_drawn)
     return true;
+
   if (!layer->scroll_children())
     return false;
   for (std::set<LayerImpl*>::const_iterator it =

[Ian Vollick, 2015/03/06 18:56:16]

Iterating over the children caused the brittleness you're fixing, no? Could we
just return layer->draw_properties().layer_or_descendant_is_draw ||
layer->scroll_children() and skip this?

[majidvp, 2015/03/06 19:43:03]

The issue was due to fact that layer was only checking itself and its
scroll children. It should have been checking itself, its descendant,
and its scroll descendant. Actually in the specific case I was testing
there was not any scroll_children() involved at all. The problem was 
caused by iframe scrolling layer being hidden itself while it
had a drawn descendant.

If we check only existence of scroll_children we may risk having 
false positive when scroll_children is actually not drawn.

            layer->scroll_children()->begin();
        it != layer->scroll_children()->end();
        ++it) {
-    if ((*it)->IsDrawnRenderSurfaceLayerListMember())
+    if ((*it)->draw_properties().layer_or_descendant_is_drawn)
       return true;
   }
   return false;