cc: Do not allow gesture-scrolling 'overflow[-{x|y}]:hidden' layers.

cc/trees/layer_tree_host_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_host_impl.h"
 
 #include <algorithm>
 #include <limits>
 
 #include "base/basictypes.h"
@@ skipping 1895 matching lines @@
 }
 
 static LayerImpl* NextScrollLayer(LayerImpl* layer) {
   if (LayerImpl* scroll_parent = layer->scroll_parent())
     return scroll_parent;
   return layer->parent();
 }
 
 LayerImpl* LayerTreeHostImpl::FindScrollLayerForDeviceViewportPoint(
     gfx::PointF device_viewport_point, InputHandler::ScrollInputType type,
-    LayerImpl* layer_impl, bool* scroll_on_main_thread) {
+    LayerImpl* layer_impl, bool* scroll_on_main_thread) const {
   DCHECK(scroll_on_main_thread);
 
   // Walk up the hierarchy and look for a scrollable layer.
   LayerImpl* potentially_scrolling_layer_impl = 0;
   for (; layer_impl; layer_impl = NextScrollLayer(layer_impl)) {
     // The content layer can also block attempts to scroll outside the main
     // thread.
     ScrollStatus status = layer_impl->TryScroll(device_viewport_point, type);
     if (status == ScrollOnMainThread) {
       *scroll_on_main_thread = true;
@@ skipping 889 matching lines @@
   std::set<UIResourceId>::iterator found_in_evicted =
       evicted_ui_resources_.find(uid);
   if (found_in_evicted == evicted_ui_resources_.end())
     return;
   evicted_ui_resources_.erase(found_in_evicted);
   if (evicted_ui_resources_.empty())
     client_->OnCanDrawStateChanged(CanDraw());
 }
 
 }  // namespace cc