Refactor unreliable hit test code to avoid owning_layers

cc/trees/layer_tree_host_impl.h

 // 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.
 
 #ifndef CC_TREES_LAYER_TREE_HOST_IMPL_H_
 #define CC_TREES_LAYER_TREE_HOST_IMPL_H_
 
 #include <stddef.h>
 
 #include <bitset>
@@ skipping 633 matching lines @@
   // Returns true if status changed.
   bool UpdateGpuRasterizationStatus();
   void UpdateTreeResourcesForGpuRasterizationIfNeeded();
 
   Viewport* viewport() const { return viewport_.get(); }
 
   InputHandler::ScrollStatus ScrollBeginImpl(
       ScrollState* scroll_state,
       LayerImpl* scrolling_layer_impl,
       InputHandler::ScrollInputType type);
+  bool IsInitialScrollHitTestReliable(LayerImpl* layer, const gfx::PointF&);
   void DistributeScrollDelta(ScrollState* scroll_state);
 
   bool AnimatePageScale(base::TimeTicks monotonic_time);
   bool AnimateScrollbars(base::TimeTicks monotonic_time);
   bool AnimateBrowserControls(base::TimeTicks monotonic_time);
 
   void TrackDamageForAllSurfaces(
       const LayerImplList& render_surface_layer_list);
 
   void UpdateTileManagerMemoryPolicy(const ManagedMemoryPolicy& policy);
@@ skipping 169 matching lines @@
 
   std::unique_ptr<PendingTreeDurationHistogramTimer>
       pending_tree_duration_timer_;
 
   DISALLOW_COPY_AND_ASSIGN(LayerTreeHostImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_LAYER_TREE_HOST_IMPL_H_