Files App: Add metrics for background performance.

FileBrowser.Load.BackgroundScript:
  Time to initialize backend script to wait for events.
FileBrowser.Load.BackgroundLaunch:
  Time from onLaunched event is called to the window is created.
FileBrowser.Load.BackgroundRestart:
  Time to create a window on restart.

BUG=675536
TEST=manually confirmed on Linux that sane values are exported in
chrome://histograms

CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2585193002
Cr-Commit-Position: refs/heads/master@{#439755}

tools/metrics/histograms/histograms.xml

@@ -110095,6 +110095,11 @@ value.
       label="Total load time from the moment the Javascript started parsing
              till the moment the empty file list is displayed."/>
   <suffix name="Script" label="Time to parse Javascript and CSS."/>
+  <suffix name="BackgroundScript"
+      label="Time to initialize backend script to wait for events."/>
+  <suffix name="BackgroundLaunch"
+      label="Time from onLaunched event is called to the window is created."/>
+  <suffix name="BackgroundRestart" label="Time to create a window on restart."/>
   <affected-histogram name="FileBrowser.Load"/>
 </histogram_suffixes>
 

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');

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

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+<include src="metrics_start.js">
 <include src="../../common/js/lru_cache.js">
 <include src="../../common/js/progress_center_common.js">
 <include src="../../common/js/importer_common.js">

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

+// 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.
+
+/**
+ * @fileoverview Metrics calls to start measurement of script loading.  Include
+ * this as the first script in background_scripts.js (i.e. after the common
+ * scripts that define the metrics namespace).
+ */
+
+metrics.startInterval('Load.BackgroundScript');