Scrollbars should get notifications from all scrollable layers up to container.

cc/trees/layer_tree_host_impl_unittest.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 <cmath>
 
 #include "base/bind.h"
 #include "base/command_line.h"
@@ skipping 1352 matching lines @@
   contents->SetBounds(content_size);
   contents->SetContentBounds(content_size);
 
   // The scrollbar is on the right side.
   scoped_ptr<PaintedScrollbarLayerImpl> scrollbar =
       PaintedScrollbarLayerImpl::Create(host_impl_->active_tree(), 5, VERTICAL);
   scrollbar->SetDrawsContent(true);
   scrollbar->SetBounds(gfx::Size(15, viewport_size.height()));
   scrollbar->SetContentBounds(gfx::Size(15, viewport_size.height()));
   scrollbar->SetPosition(gfx::Point(285, 0));
+  scrollbar->SetClipLayerById(1);
   scrollbar->SetScrollLayerById(2);
 
   scroll->AddChild(contents.Pass());
   root->AddChild(scroll.Pass());
   root->AddChild(scrollbar.PassAs<LayerImpl>());
 
   host_impl_->active_tree()->SetRootLayer(root.Pass());
   host_impl_->active_tree()->SetViewportLayersFromIds(1, 2, Layer::INVALID_ID);
   host_impl_->active_tree()->DidBecomeActive();
   DrawFrame();
@@ skipping 5003 matching lines @@
   EXPECT_EQ(host_impl_->global_tile_state().hard_memory_limit_in_bytes,
             300u * 1024u * 1024u);
   EXPECT_EQ(host_impl_->global_tile_state().soft_memory_limit_in_bytes,
             150u * 1024u * 1024u);
   EXPECT_EQ(host_impl_->global_tile_state().unused_memory_limit_in_bytes,
             75u * 1024u * 1024u);
 }
 
 }  // namespace
 }  // namespace cc