Notify page load metrics when the app enters the background.

chrome/browser/metrics/page_load_metrics_provider.cc

+// Copyright 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.
+
+#include "chrome/browser/metrics/page_load_metrics_provider.h"
+
+#include "chrome/browser/page_load_metrics/metrics_web_contents_observer.h"
+#include "chrome/browser/ui/android/tab_model/tab_model.h"
+#include "chrome/browser/ui/android/tab_model/tab_model_list.h"
+
+PageLoadMetricsProvider::PageLoadMetricsProvider() {}
+
+PageLoadMetricsProvider::~PageLoadMetricsProvider() {}
+
+void PageLoadMetricsProvider::OnAppEnterBackground() {
+  for (TabModelList::const_iterator it = TabModelList::begin();
+       it != TabModelList::end(); ++it) {
+    TabModel* model = *it;
+    for (int tab_index = 0; tab_index < model->GetTabCount(); ++tab_index) {
+      content::WebContents* web_contents = model->GetWebContentsAt(tab_index);
+      if (!web_contents)
+        continue;
+      page_load_metrics::MetricsWebContentsObserver* observer =
+          page_load_metrics::MetricsWebContentsObserver::FromWebContents(
+              web_contents);
+      if (observer)
+        observer->FlushMetricsOnAppEnterBackground();
+    }
+  }
+}