Add UMA to track app launcher discoverability.

chrome/browser/ui/ash/app_list/app_list_service_ash.cc

Index: chrome/browser/ui/ash/app_list/app_list_service_ash.cc
diff --git a/chrome/browser/ui/ash/app_list/app_list_service_ash.cc b/chrome/browser/ui/ash/app_list/app_list_service_ash.cc
index 03d23b3c95424eb792bebf63bf168f7ce02cc4d3..618633f331519d999a17399d566d7104c666027b 100644
--- a/chrome/browser/ui/ash/app_list/app_list_service_ash.cc
+++ b/chrome/browser/ui/ash/app_list/app_list_service_ash.cc
@@ -35,7 +35,8 @@ class AppListServiceAsh : public AppListServiceImpl {
   virtual void ShowForProfile(Profile* default_profile) OVERRIDE;
   virtual bool IsAppListVisible() const OVERRIDE;
   virtual void DismissAppList() OVERRIDE;
-  virtual void EnableAppList(Profile* initial_profile) OVERRIDE;
+  virtual void EnableAppList(Profile* initial_profile,
+                             AppListEnableSource enable_source) OVERRIDE;
   virtual gfx::NativeWindow GetAppListWindow() OVERRIDE;
   virtual Profile* GetCurrentAppListProfile() OVERRIDE;
   virtual AppListControllerDelegate* GetControllerDelegate() OVERRIDE;
@@ -76,7 +77,8 @@ void AppListServiceAsh::DismissAppList() {
     ash::Shell::GetInstance()->ToggleAppList(NULL);
 }
 
-void AppListServiceAsh::EnableAppList(Profile* initial_profile) {}
+void AppListServiceAsh::EnableAppList(Profile* initial_profile,
+                                      AppListEnableSource enable_source) {}
 
 gfx::NativeWindow AppListServiceAsh::GetAppListWindow() {
   if (ash::Shell::HasInstance())