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

cc/trees/layer_tree_impl.cc

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/trees/layer_tree_impl.h"
 
 #include <algorithm>
 #include <limits>
 #include <set>
 
@@ skipping 1430 matching lines @@
       ((!data_for_recursion->closest_match ||
         distance_to_intersection > data_for_recursion->closest_distance))) {
     data_for_recursion->closest_distance = distance_to_intersection;
     data_for_recursion->closest_match = layer;
   }
 }
 
 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;
 }
 
 struct FindScrollingLayerFunctor {
   bool operator()(LayerImpl* layer) const {
     return ScrollsAnyDrawnRenderSurfaceLayerListMember(layer);
   }
 };
@@ skipping 184 matching lines @@
     scoped_ptr<PendingPageScaleAnimation> pending_animation) {
   pending_page_scale_animation_ = pending_animation.Pass();
 }
 
 scoped_ptr<PendingPageScaleAnimation>
     LayerTreeImpl::TakePendingPageScaleAnimation() {
   return pending_page_scale_animation_.Pass();
 }
 
 }  // namespace cc