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

cc/trees/layer_tree_host.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.h"
 
 #include <algorithm>
 #include <stack>
 #include <string>
 
@@ skipping 124 matching lines @@
 
 void LayerTreeHost::InitializeForTesting(scoped_ptr<Proxy> proxy_for_testing) {
   InitializeProxy(proxy_for_testing.Pass());
 }
 
 void LayerTreeHost::InitializeProxy(scoped_ptr<Proxy> proxy) {
   TRACE_EVENT0("cc", "LayerTreeHost::InitializeForReal");
 
   proxy_ = proxy.Pass();
   proxy_->Start();
+  if (settings_.accelerated_animation_enabled) {
+    animation_registrar_->set_supports_scroll_animations(
+        proxy_->SupportsImplScrolling());
+  }
 }
 
 LayerTreeHost::~LayerTreeHost() {
   TRACE_EVENT0("cc", "LayerTreeHost::~LayerTreeHost");
 
   overhang_ui_resource_.reset();
 
   if (root_layer_.get())
     root_layer_->SetLayerTreeHost(NULL);
 
@@ skipping 1100 matching lines @@
   swap_promise_list_.push_back(swap_promise.Pass());
 }
 
 void LayerTreeHost::BreakSwapPromises(SwapPromise::DidNotSwapReason reason) {
   for (size_t i = 0; i < swap_promise_list_.size(); i++)
     swap_promise_list_[i]->DidNotSwap(reason);
   swap_promise_list_.clear();
 }
 
 }  // namespace cc