cc: Disallow scroll offset animations when impl-scrolling isn't supported

cc/test/fake_proxy.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/test/fake_proxy.h"
 
 namespace cc {
 
 void FakeProxy::SetLayerTreeHost(LayerTreeHost* host) {
   layer_tree_host_ = host;
@@ skipping 14 matching lines @@
 bool FakeProxy::CommitRequested() const { return false; }
 
 size_t FakeProxy::MaxPartialTextureUpdates() const {
   return max_partial_texture_updates_;
 }
 
 void FakeProxy::SetMaxPartialTextureUpdates(size_t max) {
   max_partial_texture_updates_ = max;
 }
 
+bool FakeProxy::SupportsImplScrolling() const { return false; }
+
 bool FakeProxy::CommitPendingForTesting() { return false; }
 
 scoped_ptr<base::Value> FakeProxy::AsValue() const {
   scoped_ptr<base::DictionaryValue> state(new base::DictionaryValue());
   return state.PassAs<base::Value>();
 }
 
 }  // namespace cc