Files App: add more performance metrics for foreground initialization.

FileBrowser.Load.ImportElements:
    Time to initialize the polymer elements.
FileBrowser.Load.InitBackgroundPage:
    Time to initialize the background page.
FileBrowser.Load.InitDocuments:
    Time to initialize the background page and the elements.
FileBrowser.Load.InitSettings:
    Time to restore user settings.
FileBrowser.Load.InitUI:
    Time to initialize all UI after all elements are initialized.

BUG=675536
TEST=manually confirmed on Linux that the above values are exported to chrome://histograms.

CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2589693002
Cr-Commit-Position: refs/heads/master@{#439769}

tools/metrics/histograms/histograms.xml

@@ -110100,6 +110100,15 @@ value.
   <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."/>
+  <suffix name="ImportElements"
+      label="Time to initialize the polymer elements."/>
+  <suffix name="InitBackgroundPage"
+      label="Time to initialize the background page."/>
+  <suffix name="InitDocuments"
+      label="Time to initialize the background page and the elements."/>
+  <suffix name="InitSettings" label="Time to restore user settings."/>
+  <suffix name="InitUI"
+      label="Time to initialize all UI after all elements are initialized."/>
   <affected-histogram name="FileBrowser.Load"/>
 </histogram_suffixes>
 

ui/file_manager/file_manager/foreground/js/elements_importer.js

@@ -10,11 +10,17 @@ window.Polymer.dom = 'shadow';
  *   elements for file manager UI are loaded.
  */
 window.importElementsPromise = new Promise(function(resolve, reject) {
+  var startTime = Date.now();
+
   var link = document.createElement('link');
   link.rel = 'import';
   link.href = 'foreground/elements/elements_bundle.html';
   link.setAttribute('async', '');
-  link.onload = resolve;
+  link.onload = function() {
+    chrome.metricsPrivate.recordTime(
+        'FileBrowser.Load.ImportElements', Date.now() - startTime);
+    resolve();
+  };
   link.onerror = reject;
   document.head.appendChild(link);
 });

ui/file_manager/file_manager/foreground/js/file_manager.js

@@ -466,9 +466,13 @@ FileManager.prototype = /** @struct */ {
    * @private
    */
   FileManager.prototype.startInitSettings_ = function() {
+    metrics.startInterval('Load.InitSettings');
     this.appStateController_ = new AppStateController(this.dialogType);
     return new Promise(function(resolve) {
-      this.appStateController_.loadInitialViewOptions().then(resolve);
+      this.appStateController_.loadInitialViewOptions().then(function() {
+        metrics.recordInterval('Load.InitSettings');
+        resolve();
+      });
     }.bind(this));
   };
 
@@ -715,16 +719,20 @@ FileManager.prototype = /** @struct */ {
     this.dialogDom_ = dialogDom;
     this.document_ = this.dialogDom_.ownerDocument;
 
+    metrics.startInterval('Load.InitDocuments');
     return Promise.all([
       this.initBackgroundPagePromise_,
       window.importElementsPromise
     ]).then(function() {
+      metrics.recordInterval('Load.InitDocuments');
+      metrics.startInterval('Load.InitUI');
       this.initEssentialUI_();
       this.initAdditionalUI_();
       return this.initSettingsPromise_;
     }.bind(this)).then(function() {
       this.initFileSystemUI_();
       this.initUIFocus_();
+      metrics.recordInterval('Load.InitUI');
     }.bind(this));
   };
 
@@ -770,6 +778,7 @@ FileManager.prototype = /** @struct */ {
    */
   FileManager.prototype.startInitBackgroundPage_ = function() {
     return new Promise(function(resolve) {
+      metrics.startInterval('Load.InitBackgroundPage');
       chrome.runtime.getBackgroundPage(/** @type {function(Window=)} */ (
           function(opt_backgroundPage) {
             assert(opt_backgroundPage);
@@ -787,6 +796,7 @@ FileManager.prototype = /** @struct */ {
                   this.backgroundPage_.background.mediaScanner;
               this.historyLoader_ =
                   this.backgroundPage_.background.historyLoader;
+              metrics.recordInterval('Load.InitBackgroundPage');
               resolve();
             }.bind(this));
           }.bind(this)));