Suppress scrolls that begin on fixed-pos 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 <list>
 #include <set>
 #include <string>
@@ skipping 466 matching lines @@
   void ClearCurrentlyScrollingLayer();
 
   void AnimateScrollbarsRecursive(LayerImpl* layer,
                                   base::TimeTicks time);
 
   void UpdateCurrentFrameTime(base::TimeTicks* ticks, base::Time* now) const;
 
   LayerImpl* FindScrollLayerForViewportPoint(
       gfx::Point viewport_point,
       InputHandler::ScrollInputType type,
-      bool* scroll_on_main_thread);
+      bool* scroll_on_main_thread) const;
   float DeviceSpaceDistanceToLayer(gfx::PointF device_viewport_point,
                                    LayerImpl* layer_impl);
   void StartScrollbarAnimationRecursive(LayerImpl* layer, base::TimeTicks time);
   void SetManagedMemoryPolicy(const ManagedMemoryPolicy& policy,
                               bool zero_budget);
   void EnforceManagedMemoryPolicy(const ManagedMemoryPolicy& policy);
 
   void DidInitializeVisibleTile();
 
   void MarkUIResourceNotEvicted(UIResourceId uid);
@@ skipping 124 matching lines @@
 
   // Optional callback to notify of new tree activations.
   base::Closure tree_activation_callback_;
 
   DISALLOW_COPY_AND_ASSIGN(LayerTreeHostImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_LAYER_TREE_HOST_IMPL_H_