[android] Remove unused scroll delta in TopControls

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 2567 matching lines @@
     return false;
 
   // Always consume if it's in the direction to show the top controls.
   if (scroll_delta.y() < 0)
     return true;
 
   if (CurrentlyScrollingLayer() != InnerViewportScrollLayer() &&
       CurrentlyScrollingLayer() != OuterViewportScrollLayer())
     return false;
 
+  if (scroll_delta.y() > 0 && top_controls_manager_->ContentTopOffset() == 0 &&

[jdduke (slow), 2014/10/21 16:09:10]

This is probably worth a comment along the lines of:

// Avoid confusing top controls bookkeeping with positive overscroll deltas.

[sujith, 2014/10/22 14:20:15]

Done.

+      (InnerViewportScrollLayer()->TotalScrollOffset().y() ==
+       InnerViewportScrollLayer()->MaxScrollOffset().y()))
+    return false;
+
   if (InnerViewportScrollLayer()->MaxScrollOffset().y() > 0)
     return true;
 
   if (OuterViewportScrollLayer() &&
       OuterViewportScrollLayer()->MaxScrollOffset().y() > 0)
     return true;
 
   return false;
 }
 
@@ skipping 875 matching lines @@
 }
 
 void LayerTreeHostImpl::UnregisterPictureLayerImpl(PictureLayerImpl* layer) {
   std::vector<PictureLayerImpl*>::iterator it =
       std::find(picture_layers_.begin(), picture_layers_.end(), layer);
   DCHECK(it != picture_layers_.end());
   picture_layers_.erase(it);
 }
 
 }  // namespace cc