[android] Remove unused scroll delta in TopControls

cc/trees/layer_tree_host_impl.cc

Index: cc/trees/layer_tree_host_impl.cc
diff --git a/cc/trees/layer_tree_host_impl.cc b/cc/trees/layer_tree_host_impl.cc
index c5b9566fc070a1d554a63823d31fd26135e972de..38fb9f935f3c1ec8c1ca645c13e2ab4a4bbac6b2 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -2585,6 +2585,11 @@ bool LayerTreeHostImpl::ShouldTopControlsConsumeScroll(
       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;