Add histgrams to Folder shortcut feature in Files.app.

chrome/browser/resources/file_manager/js/folder_shortcuts_data_model.js

 // Copyright (c) 2013 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.
 
 /**
  * Model for the folder shortcuts. This object is cr.ui.ArrayDataModel-like
  * object with additional methods for the folder shortcut feature.
  * This uses chrome.storage as backend. Items are always sorted by file path.
  *
  * @constructor
@@ skipping 17 matching lines @@
   chrome.storage.sync.get(FolderShortcutsDataModel.NAME, function(value) {
     if (!(FolderShortcutsDataModel.NAME in value))
       return;
 
     // Since the value comes from outer resource, we have to check it just in
     // case.
     var list = value[FolderShortcutsDataModel.NAME];
     if (list instanceof Array) {
       list = filter(list);
 
+      // Record metrics.
+      metrics.recordSmallCount('FolderShortcut.Count', list.length);
+
       var permutation = this.calculatePermitation_(this.array_, list);
       this.array_ = list;
       this.firePermutedEvent_(permutation);
     }
   }.bind(this));
 
   // Listening for changes in the storage.
   chrome.storage.onChanged.addListener(function(changes, namespace) {
     if (!(FolderShortcutsDataModel.NAME in changes) || namespace != 'sync')
       return;
@@ skipping 105 matching lines @@
     }
     // If value is not added yet, add it at the last.
     if (addedIndex == -1) {
       this.array_.push(value);
       addedIndex = this.length;
     }
 
     this.firePermutedEvent_(
         this.calculatePermitation_(oldArray, this.array_));
     this.save_();
+    metrics.recordUserAction('FolderShortcut.Add');
     return addedIndex;
   },
 
   /**
    * Removes the given item from the array.
    * @param {string} value Value to be removed from the array.
    * @return {number} Index in the list which the element removed from.
    */
   remove: function(value) {
     var removedIndex = -1;
     var oldArray = this.array_.slice(0);  // Shallow copy.
     for (var i = 0; i < this.length; i++) {
       // Same item check: must be exact match.
       if (this.array_[i] == value) {
         this.array_.splice(i, 1);
         removedIndex = i;
         break;
       }
     }
 
     if (removedIndex != -1) {
       this.firePermutedEvent_(
           this.calculatePermitation_(oldArray, this.array_));
       this.save_();
+      metrics.recordUserAction('FolderShortcut.Remove');
       return removedIndex;
     }
 
     // No item is removed.
     return -1;
   },
 
   /**
    * @param {string} path Path to be checked.
    * @return {boolean} True if the given |path| exists in the array. False
@@ skipping 70 matching lines @@
     this.dispatchEvent(permutedEvent);
 
     // Note: This model only fires 'permuted' event, because:
     // 1) 'change' event is not necessary to fire since it is covered by
     //    'permuted' event.
     // 2) 'splice' and 'sorted' events are not implemented. These events are
     //    not used in NavigationListModel. We have to implement them when
     //    necessary.
   }
 };