Add UMA for app info dialog

chrome/browser/ui/apps/app_info_dialog.h

 // Copyright 2014 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.
 
 #ifndef CHROME_BROWSER_UI_APPS_APP_INFO_DIALOG_H_
 #define CHROME_BROWSER_UI_APPS_APP_INFO_DIALOG_H_
 
 class AppListControllerDelegate;
 class Profile;
 
 namespace extensions {
 class Extension;
 }
 
+// Used for UMA to track where the App Info dialog is launched from.
+enum AppInfoDialogLaunchSource {

[benwells, 2014/08/04 02:31:59]

Why is INVALID needed?

+  INVALID,
+  FROM_APP_LIST,  // Launched from the app list context menu.
+  NUM_LAUNCH_SOURCES
+};
+
 // Shows the chrome app information dialog box.
 void ShowAppInfoDialog(AppListControllerDelegate* app_list_controller_delegate,
                        Profile* profile,
                        const extensions::Extension* app);
 
 #endif  // CHROME_BROWSER_UI_APPS_APP_INFO_DIALOG_H_