Notify page load metrics when the app enters the background.

chrome/browser/page_load_metrics/page_load_metrics_browsertest.cc

Index: chrome/browser/page_load_metrics/page_load_metrics_browsertest.cc
diff --git a/chrome/browser/page_load_metrics/page_load_metrics_browsertest.cc b/chrome/browser/page_load_metrics/page_load_metrics_browsertest.cc
index ddd6cb8957531a8b6c00a4f6c600fb4849e6b2ff..f10fe938396f34791f08543fe05d60b8468faa5f 100644
--- a/chrome/browser/page_load_metrics/page_load_metrics_browsertest.cc
+++ b/chrome/browser/page_load_metrics/page_load_metrics_browsertest.cc
@@ -4,8 +4,11 @@
 
 #include "base/macros.h"
 #include "base/test/histogram_tester.h"
+#include "chrome/browser/page_load_metrics/metrics_web_contents_observer.h"
 #include "chrome/browser/page_load_metrics/observers/core_page_load_metrics_observer.h"
 #include "chrome/browser/page_load_metrics/observers/document_write_page_load_metrics_observer.h"
+#include "chrome/browser/ui/browser.h"
+#include "chrome/browser/ui/tabs/tab_strip_model.h"
 #include "chrome/common/url_constants.h"
 #include "chrome/test/base/in_process_browser_test.h"
 #include "chrome/test/base/ui_test_utils.h"
@@ -35,6 +38,22 @@ IN_PROC_BROWSER_TEST_F(MetricsWebContentsObserverBrowserTest, NoNavigation) {
   histogram_tester_.ExpectTotalCount(internal::kHistogramFirstLayout, 0);
 }
 
+IN_PROC_BROWSER_TEST_F(MetricsWebContentsObserverBrowserTest, GetAllObservers) {
+  ASSERT_TRUE(embedded_test_server()->Start());
+
+  ASSERT_FALSE(
+      page_load_metrics::MetricsWebContentsObserver::GetAllObservers().empty());
+
+  TabStripModel* tab_strip_model = browser()->tab_strip_model();
+  content::WebContentsDestroyedWatcher destroyed_watcher(
+      tab_strip_model->GetActiveWebContents());
+  tab_strip_model->CloseAllTabs();
+  destroyed_watcher.Wait();
+
+  ASSERT_TRUE(
+      page_load_metrics::MetricsWebContentsObserver::GetAllObservers().empty());
+}
+
 IN_PROC_BROWSER_TEST_F(MetricsWebContentsObserverBrowserTest, NewPage) {
   ASSERT_TRUE(embedded_test_server()->Start());