[Prerender] first contentful paint histograms.

chrome/browser/prerender/prerender_test_utils.h

 // Copyright (c) 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_PRERENDER_PRERENDER_TEST_UTILS_H_
 #define CHROME_BROWSER_PRERENDER_PRERENDER_TEST_UTILS_H_
 
 #include <deque>
 #include <functional>
 #include <memory>
@@ skipping 219 matching lines @@
   void MarkDestruction(FinalStatus reason);
 
   base::RunLoop wait_loop_;
   FinalStatus expected_final_status_;
   bool saw_correct_status_;
   std::unique_ptr<DestructionMarker> marker_;
 
   DISALLOW_COPY_AND_ASSIGN(DestructionWaiter);
 };
 
+// Wait until a PrerenderManager has seen a first contentful paint.
+class FirstContentfulPaintManagerWaiter : public PrerenderManagerObserver {
+ public:
+  // Create and return a pointer to a |FirstContentfulPaintManagerWaiter|. The
+  // instance is owned by the |PrerenderManager|.
+  static FirstContentfulPaintManagerWaiter* Create(PrerenderManager* manager);
+
+  ~FirstContentfulPaintManagerWaiter() override;
+
+  void OnFirstContentfulPaint() override;
+
+  // Wait for a first contentful paint to be seen by our PrerenderManager.
+  void Wait();
+
+ private:
+  FirstContentfulPaintManagerWaiter();
+
+  std::unique_ptr<base::RunLoop> waiter_;
+  bool saw_fcp_;
+
+  DISALLOW_COPY_AND_ASSIGN(FirstContentfulPaintManagerWaiter);
+};
+
 // PrerenderContentsFactory that uses TestPrerenderContents.
 class TestPrerenderContentsFactory : public PrerenderContents::Factory {
  public:
   TestPrerenderContentsFactory();
 
   ~TestPrerenderContentsFactory() override;
 
   std::unique_ptr<TestPrerender> ExpectPrerenderContents(
       FinalStatus final_status);
 
@@ skipping 135 matching lines @@
 // |file| afterwards. When the first load has been scheduled, runs |callback| on
 // the UI thread.
 void CreateHangingFirstRequestInterceptorOnIO(
     const GURL& url, const base::FilePath& file, base::Closure callback);
 
 }  // namespace test_utils
 
 }  // namespace prerender
 
 #endif  // CHROME_BROWSER_PRERENDER_PRERENDER_TEST_UTILS_H_