Buffer cross frame paint timing updates.

chrome/browser/page_load_metrics/page_load_metrics_embedder_interface.h

 // Copyright 2016 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.
 
 #ifndef CHROME_BROWSER_PAGE_LOAD_METRICS_PAGE_LOAD_METRICS_EMBEDDER_INTERFACE_H_
 #define CHROME_BROWSER_PAGE_LOAD_METRICS_PAGE_LOAD_METRICS_EMBEDDER_INTERFACE_H_
 
+#include <memory>
+
 class GURL;
 
+namespace base {
+class Timer;
+}  // namespace base
+
 namespace page_load_metrics {
 
 class PageLoadTracker;
 
 // This class serves as a functional interface to various chrome// features.
 // Impl version is defined in chrome/browser/page_load_metrics.
 class PageLoadMetricsEmbedderInterface {
  public:
   virtual ~PageLoadMetricsEmbedderInterface() {}
   virtual bool IsNewTabPageUrl(const GURL& url) = 0;
   virtual void RegisterObservers(PageLoadTracker* metrics) = 0;
+  virtual std::unique_ptr<base::Timer> CreateTimer() = 0;
 };
 
 }  // namespace page_load_metrics
 
 #endif  // CHROME_BROWSER_PAGE_LOAD_METRICS_PAGE_LOAD_METRICS_EMBEDDER_INTERFACE_H_