Add UMA to track app launcher discoverability.

chrome/browser/ui/app_list/app_list_service_mac.mm

 // Copyright 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.
 
 #import "chrome/browser/ui/app_list/app_list_service_mac.h"
 
 #include <ApplicationServices/ApplicationServices.h>
 #import <Cocoa/Cocoa.h>
 
 #include "apps/app_shim/app_shim_mac.h"
@@ skipping 424 matching lines @@
   [animation_controller_ animateWindow:[window_controller_ window]
                           targetOrigin:last_start_origin_
                                closing:YES];
 }
 
 bool AppListServiceMac::IsAppListVisible() const {
   return [[window_controller_ window] isVisible] &&
       ![animation_controller_ isClosing];
 }
 
-void AppListServiceMac::EnableAppList(Profile* initial_profile) {
-  AppListServiceImpl::EnableAppList(initial_profile);
+void AppListServiceMac::EnableAppList(Profile* initial_profile,
+                                      AppListEnableSource enable_source) {
+  AppListServiceImpl::EnableAppList(initial_profile, enable_source);
   AppController* controller = [NSApp delegate];
   [controller initAppShimMenuController];
 }
 
 void AppListServiceMac::CreateShortcut() {
   CreateAppListShim(GetProfilePath(
       g_browser_process->profile_manager()->user_data_dir()));
 }
 
 NSWindow* AppListServiceMac::GetAppListWindow() {
@@ skipping 137 matching lines @@
 
 - (void)animationDidEnd:(NSAnimation*)animation {
   content::BrowserThread::PostTask(
       content::BrowserThread::UI,
       FROM_HERE,
       base::Bind(&AppListServiceMac::WindowAnimationDidEnd,
                  base::Unretained(AppListServiceMac::GetInstance())));
 }
 
 @end