Convert enable_one_click_signin to new buildflag system

chrome/browser/ui/cocoa/browser_window_cocoa.mm

Index: chrome/browser/ui/cocoa/browser_window_cocoa.mm
diff --git a/chrome/browser/ui/cocoa/browser_window_cocoa.mm b/chrome/browser/ui/cocoa/browser_window_cocoa.mm
index c42564373f918ae159be7aef1a4ebe151de622a3..f0463f818e63fdb499887fe320e873679d2a8bf9 100644
--- a/chrome/browser/ui/cocoa/browser_window_cocoa.mm
+++ b/chrome/browser/ui/cocoa/browser_window_cocoa.mm
@@ -53,6 +53,7 @@
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
 #include "chrome/browser/web_applications/web_app.h"
 #include "chrome/common/chrome_switches.h"
+#include "chrome/common/features.h"
 #include "chrome/common/pref_names.h"
 #include "chrome/grit/generated_resources.h"
 #include "components/bookmarks/common/bookmark_pref_names.h"
@@ -71,7 +72,7 @@
 #include "ui/events/keycodes/keyboard_codes.h"
 #include "ui/gfx/geometry/rect.h"
 
-#if defined(ENABLE_ONE_CLICK_SIGNIN)
+#if BUILDFLAG(ENABLE_ONE_CLICK_SIGNIN)
 #import "chrome/browser/ui/cocoa/one_click_signin_bubble_controller.h"
 #import "chrome/browser/ui/cocoa/one_click_signin_dialog_controller.h"
 #endif
@@ -641,7 +642,7 @@ void BrowserWindowCocoa::ShowTranslateBubble(
                                        errorType:error_type];
 }
 
-#if defined(ENABLE_ONE_CLICK_SIGNIN)
+#if BUILDFLAG(ENABLE_ONE_CLICK_SIGNIN)
 void BrowserWindowCocoa::ShowOneClickSigninBubble(
     OneClickSigninBubbleType type,
     const base::string16& email,