mash: Use ChromeLauncherControllerImpl, remove Mus subclass stub.

chrome/browser/ui/ash/launcher/extension_launcher_context_menu.cc

Index: chrome/browser/ui/ash/launcher/extension_launcher_context_menu.cc
diff --git a/chrome/browser/ui/ash/launcher/extension_launcher_context_menu.cc b/chrome/browser/ui/ash/launcher/extension_launcher_context_menu.cc
index 86c82de18cbc0f3713ff6b3aa7b73e40e86c2153..0214be5047a99ee5c7a2cf884f17e7917eaa706c 100644
--- a/chrome/browser/ui/ash/launcher/extension_launcher_context_menu.cc
+++ b/chrome/browser/ui/ash/launcher/extension_launcher_context_menu.cc
@@ -4,7 +4,6 @@
 
 #include "chrome/browser/ui/ash/launcher/extension_launcher_context_menu.h"
 
-#include "ash/shell.h"
 #include "base/bind.h"
 #include "chrome/browser/extensions/context_menu_matcher.h"
 #include "chrome/browser/extensions/extension_util.h"
@@ -83,7 +82,7 @@ void ExtensionLauncherContextMenu::Init() {
       AddItemWithStringId(MENU_NEW_INCOGNITO_WINDOW,
                           IDS_APP_LIST_NEW_INCOGNITO_WINDOW);
     }
-    if (!BrowserShortcutLauncherItemController(ash::Shell::Get()->shelf_model())
+    if (!BrowserShortcutLauncherItemController(controller()->shelf_model())
              .IsListOfActiveBrowserEmpty()) {
       AddItem(MENU_CLOSE,
               l10n_util::GetStringUTF16(IDS_LAUNCHER_CONTEXT_MENU_CLOSE));