Remove useless includes to ash_util.h

chrome/browser/signin/signin_error_notifier_ash_unittest.cc

Index: chrome/browser/signin/signin_error_notifier_ash_unittest.cc
diff --git a/chrome/browser/signin/signin_error_notifier_ash_unittest.cc b/chrome/browser/signin/signin_error_notifier_ash_unittest.cc
index 7d0d73a33cdd2fb4997d5938f11da4f8bd11ccd4..3c179b34764a044f8ac520757a6a7188b06d1bf6 100644
--- a/chrome/browser/signin/signin_error_notifier_ash_unittest.cc
+++ b/chrome/browser/signin/signin_error_notifier_ash_unittest.cc
@@ -29,7 +29,6 @@
 #include "ui/message_center/notification.h"
 
 #if defined(OS_WIN)
-#include "chrome/browser/ui/ash/ash_util.h"
 #include "ui/aura/test/test_screen.h"
 #include "ui/display/screen.h"
 #endif
@@ -48,7 +47,7 @@ static const char kTestAccountId[] = "testuser@test.com";
 
 // Notification ID corresponding to kProfileSigninNotificationId +
 // kTestAccountId.
-static const std::string kNotificationId =
+static const char kNotificationId[] =
     "chrome://settings/signin/testuser@test.com";
 }