Notify page load metrics when the app enters the background.

chrome/browser/page_load_metrics/metrics_web_contents_observer_unittest.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 "chrome/browser/page_load_metrics/metrics_web_contents_observer.h"
 
 #include <memory>
 #include <vector>
 
 #include "base/macros.h"
@@ skipping 454 matching lines @@
   web_contents_tester->StartNavigation(GURL(kDefaultTestUrl));
   rfh_tester->SimulateNavigationError(GURL(kDefaultTestUrl), net::ERR_ABORTED);
   rfh_tester->SimulateNavigationStop();
 
   web_contents()->Stop();
 
   histogram_tester_.ExpectTotalCount(internal::kAbortChainSizeNoCommit, 1);
   histogram_tester_.ExpectBucketCount(internal::kAbortChainSizeNoCommit, 3, 1);
 }
 
+TEST_F(MetricsWebContentsObserverTest, FlushMetricsOnAppEnterBackground) {
+  content::WebContentsTester* web_contents_tester =
+      content::WebContentsTester::For(web_contents());
+  web_contents_tester->NavigateAndCommit(GURL(kDefaultTestUrl));
+
+  histogram_tester_.ExpectTotalCount(
+      internal::kPageLoadCompletedAfterAppBackground, 0);
+
+  observer_->FlushMetricsOnAppEnterBackground();
+
+  histogram_tester_.ExpectTotalCount(
+      internal::kPageLoadCompletedAfterAppBackground, 1);
+  histogram_tester_.ExpectBucketCount(
+      internal::kPageLoadCompletedAfterAppBackground, false, 1);
+  histogram_tester_.ExpectBucketCount(
+      internal::kPageLoadCompletedAfterAppBackground, true, 0);
+
+  observer_.reset();
+
+  histogram_tester_.ExpectTotalCount(
+      internal::kPageLoadCompletedAfterAppBackground, 2);
+  histogram_tester_.ExpectBucketCount(
+      internal::kPageLoadCompletedAfterAppBackground, false, 1);
+  histogram_tester_.ExpectBucketCount(
+      internal::kPageLoadCompletedAfterAppBackground, true, 1);
+}
+
 }  // namespace page_load_metrics