Hide scrollbars when their dimensions are not scrollable.

cc/layers/layer_impl.cc

 // Copyright 2012 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/layers/layer_impl.h"
 
 #include "base/debug/trace_event.h"
 #include "base/debug/trace_event_argument.h"
 #include "base/json/json_reader.h"
 #include "base/strings/stringprintf.h"
@@ skipping 365 matching lines @@
       ScrollDelta() + scroll - new_delta;
   SetScrollDelta(new_delta);
 
   return unscrolled;
 }
 
 void LayerImpl::SetScrollClipLayer(int scroll_clip_layer_id) {
   scroll_clip_layer_ = layer_tree_impl()->LayerById(scroll_clip_layer_id);
 }
 
+bool LayerImpl::user_scrollable(ScrollbarOrientation orientation) const {
+  return (orientation == HORIZONTAL) ? user_scrollable_horizontal_
+                                     : user_scrollable_vertical_;
+}
+
 void LayerImpl::ApplySentScrollDeltasFromAbortedCommit() {
   // Pending tree never has sent scroll deltas
   DCHECK(layer_tree_impl()->IsActiveTree());
 
   // Apply sent scroll deltas to scroll position / scroll delta as if the
   // main thread had applied them and then committed those values.
   //
   // This function should not change the total scroll offset; it just shifts
   // some of the scroll delta to the scroll offset.  Therefore, adjust these
   // variables directly rather than calling the scroll offset delegate to
@@ skipping 1160 matching lines @@
 }
 
 void LayerImpl::NotifyAnimationFinished(
     base::TimeTicks monotonic_time,
     Animation::TargetProperty target_property) {
   if (target_property == Animation::ScrollOffset)
     layer_tree_impl_->InputScrollAnimationFinished();
 }
 
 }  // namespace cc