Ensure that render surface layer list is not dirty/empty before hit testing for touch events

cc/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/layer_tree_host_impl.h"
 
 #include <algorithm>
 
 #include "base/basictypes.h"
 #include "base/debug/trace_event.h"
@@ skipping 358 matching lines @@
     m_client->setNeedsCommitOnImplThread();
 }
 
 void LayerTreeHostImpl::scheduleAnimation()
 {
     m_client->setNeedsRedrawOnImplThread();
 }
 
 bool LayerTreeHostImpl::haveTouchEventHandlersAt(const gfx::Point& viewportPoint)
 {
+    if (!ensureRenderSurfaceLayerList())
+      return false;
 
     gfx::PointF deviceViewportPoint = gfx::ScalePoint(viewportPoint, m_deviceScaleFactor);
 
     // First find out which layer was hit from the saved list of visible layers
     // in the most recent frame.
     LayerImpl* layerImpl = LayerTreeHostCommon::findLayerThatIsHitByPoint(deviceViewportPoint, activeTree()->RenderSurfaceLayerList());
 
     // Walk up the hierarchy and look for a layer with a touch event handler region that the given point hits.
     for (; layerImpl; layerImpl = layerImpl->parent()) {
       if (LayerTreeHostCommon::layerHasTouchEventHandlersAt(deviceViewportPoint,layerImpl))
@@ skipping 1312 matching lines @@
     ScrollbarAnimationController* scrollbarController = layer->scrollbarAnimationController();
     double monotonicTime = (time - base::TimeTicks()).InSecondsF();
     if (scrollbarController && scrollbarController->animate(monotonicTime))
         m_client->setNeedsRedrawOnImplThread();
 
     for (size_t i = 0; i < layer->children().size(); ++i)
         animateScrollbarsRecursive(layer->children()[i], time);
 }
 
 }  // namespace cc