Clear renderer compositor trees if new page does not render in 4 seconds

cc/trees/proxy_main.cc

 // Copyright 2015 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/proxy_main.h"
 
 #include <algorithm>
 #include <string>
 
 #include "base/memory/ptr_util.h"
@@ skipping 466 matching lines @@
 }
 
 bool ProxyMain::IsImplThread() const {
   return task_runner_provider_->IsImplThread();
 }
 
 base::SingleThreadTaskRunner* ProxyMain::ImplThreadTaskRunner() {
   return task_runner_provider_->ImplThreadTaskRunner();
 }
 
+void ProxyMain::ResetTrees() {
+  DCHECK(IsMainThread());
+  ImplThreadTaskRunner()->PostTask(
+      FROM_HERE,
+      base::Bind(&ProxyImpl::ResetTrees, base::Unretained(proxy_impl_.get())));
+}
+
 }  // namespace cc