chrome: Cleanup class/struct forward declarations

chrome/browser/notifications/notification_delegate.h

Index: chrome/browser/notifications/notification_delegate.h
diff --git a/chrome/browser/notifications/notification_delegate.h b/chrome/browser/notifications/notification_delegate.h
index c478869441e5778ce2071ecca485979ec8ec5926..1be79e8c3dbacd5f411a2db01efc8cab7b736467 100644
--- a/chrome/browser/notifications/notification_delegate.h
+++ b/chrome/browser/notifications/notification_delegate.h
@@ -10,10 +10,6 @@
 #include "base/memory/ref_counted.h"
 #include "ui/message_center/notification_delegate.h"
 
-namespace content {
-class WebContents;
-}
-
 // Delegate for a notification. This class has two roles: to implement callback
 // methods for notification, and to provide an identity of the associated
 // notification.