Let LayerTreeHostImpl::ScrollAnimated scroll the outer viewport.

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 <algorithm>
 #include <cmath>
 
 #include "base/bind.h"
@@ skipping 8161 matching lines @@
                                          external_viewport,
                                          external_transform,
                                          resourceless_software_draw);
   DrawFrame();
   EXPECT_TRANSFORMATION_MATRIX_EQ(
       external_transform, layer->draw_properties().target_space_transform);
 }
 
 TEST_F(LayerTreeHostImplTest, ScrollAnimated) {
   SetupScrollAndContentsLayers(gfx::Size(100, 200));
+
+  // Shrink the outer viewport clip layer so that the outer viewport can scroll.
+  host_impl_->OuterViewportScrollLayer()->parent()->SetBounds(
+      gfx::Size(50, 100));
+
   DrawFrame();
 
   base::TimeTicks start_time =
       base::TimeTicks() + base::TimeDelta::FromMilliseconds(100);
 
   BeginFrameArgs begin_frame_args =
       CreateBeginFrameArgsForTesting(BEGINFRAME_FROM_HERE);
 
   EXPECT_EQ(InputHandler::SCROLL_STARTED,
             host_impl_->ScrollAnimated(gfx::Point(), gfx::Vector2d(0, 50)));
 
   LayerImpl* scrolling_layer = host_impl_->CurrentlyScrollingLayer();
+  EXPECT_EQ(host_impl_->OuterViewportScrollLayer(), scrolling_layer);
 
   begin_frame_args.frame_time = start_time;
   host_impl_->WillBeginImplFrame(begin_frame_args);
   host_impl_->Animate();
   host_impl_->UpdateAnimationState(true);
 
   EXPECT_EQ(gfx::ScrollOffset(), scrolling_layer->CurrentScrollOffset());
   host_impl_->DidFinishImplFrame();
 
   begin_frame_args.frame_time =
@@ skipping 564 matching lines @@
   host_impl_->ActivateSyncTree();
   host_impl_->active_tree()->UpdateDrawProperties(false);
   active_tree_node =
       host_impl_->active_tree()->property_trees()->transform_tree.Node(
           page_scale_layer->transform_tree_index());
   EXPECT_EQ(active_tree_node->data.post_local_scale_factor, 2.f);
 }
 
 }  // namespace
 }  // namespace cc