Add new background abort type.

chrome/browser/page_load_metrics/page_load_metrics_observer.h

 // Copyright 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.
 
 #ifndef CHROME_BROWSER_PAGE_LOAD_METRICS_PAGE_LOAD_METRICS_OBSERVER_H_
 #define CHROME_BROWSER_PAGE_LOAD_METRICS_PAGE_LOAD_METRICS_OBSERVER_H_
 
 #include "base/macros.h"
 #include "base/optional.h"
 #include "chrome/common/page_load_metrics/page_load_timing.h"
@@ skipping 14 matching lines @@
   ABORT_RELOAD,
 
   // The user presses the back/forward button.
   ABORT_FORWARD_BACK,
 
   // The navigation is replaced with a navigation with the qualifier
   // ui::PAGE_TRANSITION_CLIENT_REDIRECT, which is caused by Javascript, or the
   // meta refresh tag.
   ABORT_CLIENT_REDIRECT,
 
-  // If the navigation is replaced by a new navigation. This includes link
+  // If the page load is replaced by a new navigation. This includes link
   // clicks, typing in the omnibox (not a reload), and form submissions.
   ABORT_NEW_NAVIGATION,
 
   // If the user presses the stop X button.
   ABORT_STOP,
 
-  // If the navigation is aborted by closing the tab or browser.
+  // If the page load is aborted by closing the tab or browser.
   ABORT_CLOSE,
 
-  // We don't know why the navigation aborted. This is the value we assign to an
+  // The page load was backgrounded, e.g. the browser was minimized or the user
+  // switched tabs. Note that the same page may be foregrounded in the future,
+  // so this is not a 'terminal' abort type.
+  ABORT_BACKGROUND,
+
+  // We don't know why the page load aborted. This is the value we assign to an
   // aborted load if the only signal we get is a provisional load finishing
   // without committing, either without error or with net::ERR_ABORTED.
   ABORT_OTHER,
 
   // Add values before this final count.
   ABORT_LAST_ENTRY
 };
 
 // Information related to failed provisional loads.
 struct FailedProvisionalLoadInfo {
@@ skipping 200 matching lines @@
   // OnFailedProvisionalLoad is invoked for tracked page loads that did not
   // commit, immediately before the observer is deleted.
   virtual void OnFailedProvisionalLoad(
       const FailedProvisionalLoadInfo& failed_provisional_load_info,
       const PageLoadExtraInfo& extra_info) {}
 };
 
 }  // namespace page_load_metrics
 
 #endif  // CHROME_BROWSER_PAGE_LOAD_METRICS_PAGE_LOAD_METRICS_OBSERVER_H_