Added some browsertests to PageLoadMetrics change

chrome/browser/page_load_metrics/page_load_metrics_browsertest.cc

 // Copyright (c) 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 "base/test/histogram_tester.h"
 #include "chrome/test/base/in_process_browser_test.h"
 #include "chrome/test/base/ui_test_utils.h"
 #include "net/test/spawned_test_server/spawned_test_server.h"
 
 namespace page_load_metrics {
 
 class MetricsWebContentsObserverBrowserTest : public InProcessBrowserTest {
  public:
   const char* kHistogramNameFirstLayout =
-      "PageLoad.Timing.NavigationToFirstLayout";
+      "PageLoad.Timing2.NavigationToFirstLayout";
   const char* kHistogramNameDomContent =
-      "PageLoad.Timing.NavigationToDOMContentLoadedEventFired";
-  const char* kHistogramNameLoad = "PageLoad.Timing.NavigationToLoadEventFired";
+      "PageLoad.Timing2.NavigationToDOMContentLoadedEventFired";
+  const char* kHistogramNameLoad =
+      "PageLoad.Timing2.NavigationToLoadEventFired";
   MetricsWebContentsObserverBrowserTest() {};
   ~MetricsWebContentsObserverBrowserTest() override {};
 
  protected:
   base::HistogramTester histogram_tester_;
 
   DISALLOW_COPY_AND_ASSIGN(MetricsWebContentsObserverBrowserTest);
 };
 
 IN_PROC_BROWSER_TEST_F(MetricsWebContentsObserverBrowserTest, NoNavigation) {
@@ skipping 26 matching lines @@
                                test_server()->GetURL("/title1.html#hash"));
   ui_test_utils::NavigateToURL(browser(),
                                test_server()->GetURL("/title2.html"));
 
   histogram_tester_.ExpectTotalCount(kHistogramNameDomContent, 1);
   histogram_tester_.ExpectTotalCount(kHistogramNameLoad, 1);
   histogram_tester_.ExpectTotalCount(kHistogramNameFirstLayout, 1);
 }
 
 }  // namespace page_load_metrics