Add histgrams to Folder shortcut feature in Files.app.

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

Index: chrome/browser/resources/file_manager/js/folder_shortcuts_data_model.js
diff --git a/chrome/browser/resources/file_manager/js/folder_shortcuts_data_model.js b/chrome/browser/resources/file_manager/js/folder_shortcuts_data_model.js
index 25895f93f608a35a20bb476a5aa218b20ac9d600..a27e5ce3e2d8d9a8e5a3d73e55989da4d5bd8d23 100644
--- a/chrome/browser/resources/file_manager/js/folder_shortcuts_data_model.js
+++ b/chrome/browser/resources/file_manager/js/folder_shortcuts_data_model.js
@@ -35,6 +35,9 @@ function FolderShortcutsDataModel() {
     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);
@@ -160,6 +163,7 @@ FolderShortcutsDataModel.prototype = {
     this.firePermutedEvent_(
         this.calculatePermitation_(oldArray, this.array_));
     this.save_();
+    metrics.recordUserAction('FolderShortcut.Add');
     return addedIndex;
   },
 
@@ -184,6 +188,7 @@ FolderShortcutsDataModel.prototype = {
       this.firePermutedEvent_(
           this.calculatePermitation_(oldArray, this.array_));
       this.save_();
+      metrics.recordUserAction('FolderShortcut.Remove');
       return removedIndex;
     }