Files App: Add metrics for background performance.

ui/file_manager/file_manager/background/js/background.js

Index: ui/file_manager/file_manager/background/js/background.js
diff --git a/ui/file_manager/file_manager/background/js/background.js b/ui/file_manager/file_manager/background/js/background.js
index ee0414d9a891ce82b2c6610872cc5e0d6b07da4a..251150d171b4cd8a89dd83a76e96d015da541505 100644
--- a/ui/file_manager/file_manager/background/js/background.js
+++ b/ui/file_manager/file_manager/background/js/background.js
@@ -462,6 +462,7 @@ FileBrowserBackground.prototype.onExecute_ = function(action, details) {
  * @override
  */
 FileBrowserBackground.prototype.onLaunched_ = function() {
+  metrics.startInterval('Load.BackgroundLaunch');
   this.initializationPromise_.then(function() {
     if (nextFileManagerWindowID == 0) {
       // The app just launched. Remove window state records that are not needed
@@ -475,7 +476,9 @@ FileBrowserBackground.prototype.onLaunched_ = function() {
         }
       });
     }
-    launchFileManager(null, undefined, LaunchType.FOCUS_ANY_OR_CREATE);
+    launchFileManager(
+        null, undefined, LaunchType.FOCUS_ANY_OR_CREATE,
+        function() { metrics.recordInterval('Load.BackgroundLaunch'); });
   });
 };
 
@@ -507,10 +510,13 @@ FileBrowserBackground.prototype.onRestarted_ = function() {
       if (items.hasOwnProperty(key)) {
         var match = key.match(FILES_ID_PATTERN);
         if (match) {
+          metrics.startInterval('Load.BackgroundRestart');
           var id = Number(match[1]);
           try {
             var appState = /** @type {Object} */ (JSON.parse(items[key]));
-            launchFileManager(appState, id);
+            launchFileManager(appState, id, undefined, function() {
+              metrics.recordInterval('Load.BackgroundRestart');
+            });
           } catch (e) {
             console.error('Corrupt launch data for ' + id);
           }
@@ -626,3 +632,4 @@ FileBrowserBackground.prototype.initContextMenu_ = function() {
  * @type {FileBrowserBackground}
  */
 window.background = new FileBrowserBackground();
+metrics.recordInterval('Load.BackgroundScript');