[Prerender] first contentful paint histograms.

chrome/browser/prerender/prerender_test_utils.h

Index: chrome/browser/prerender/prerender_test_utils.h
diff --git a/chrome/browser/prerender/prerender_test_utils.h b/chrome/browser/prerender/prerender_test_utils.h
index d7f4af8de292a2d9585e96eb596dcaeefde913c7..aed9d2cd469cf0fff467fde79a69b2d87b985508 100644
--- a/chrome/browser/prerender/prerender_test_utils.h
+++ b/chrome/browser/prerender/prerender_test_utils.h
@@ -17,6 +17,7 @@
 #include "base/run_loop.h"
 #include "base/test/histogram_tester.h"
 #include "chrome/browser/external_protocol/external_protocol_handler.h"
+#include "chrome/browser/page_load_metrics/observers/prerender_page_load_metrics_observer.h"
 #include "chrome/browser/prerender/prerender_contents.h"
 #include "chrome/browser/prerender/prerender_manager.h"
 #include "chrome/browser/safe_browsing/test_safe_browsing_service.h"
@@ -242,6 +243,26 @@ class DestructionWaiter {
   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();
+
+  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_;
+};
+
 // PrerenderContentsFactory that uses TestPrerenderContents.
 class TestPrerenderContentsFactory : public PrerenderContents::Factory {
  public:
@@ -368,6 +389,22 @@ class PrerenderInProcessBrowserTest : virtual public InProcessBrowserTest {
   DISALLOW_COPY_AND_ASSIGN(PrerenderInProcessBrowserTest);
 };
 
+// A test observer that allows the observed navigation start time to be set.
+class TestPrerenderPageLoadMetricsObserver
+    : public PrerenderPageLoadMetricsObserver {
+ public:
+  using PrerenderPageLoadMetricsObserver::PrerenderPageLoadMetricsObserver;
+
+  void SetNavigationStartMilliseconds(int ms) {
+    SetNavigationStartTicksForTesting(base::TimeTicks() +
+                                      base::TimeDelta::FromMilliseconds(ms));
+  }
+
+  void SetNavigationStartFromZero(base::TimeDelta delta) {
+    SetNavigationStartTicksForTesting(base::TimeTicks() + delta);
+  }
+};
+
 // Makes |url| respond to requests with the contents of |file|, counting the
 // number that start in |counter|.
 void CreateCountingInterceptorOnIO(