Mojo C++ bindings: extract code shared by different variants.

third_party/WebKit/Source/modules/notifications/NotificationManager.h

Index: third_party/WebKit/Source/modules/notifications/NotificationManager.h
diff --git a/third_party/WebKit/Source/modules/notifications/NotificationManager.h b/third_party/WebKit/Source/modules/notifications/NotificationManager.h
index d4b46f39331fae1e1bc863ffe6878be432526c18..071633418e6c6d5a242832d13ea2dd60b19ce822 100644
--- a/third_party/WebKit/Source/modules/notifications/NotificationManager.h
+++ b/third_party/WebKit/Source/modules/notifications/NotificationManager.h
@@ -13,12 +13,6 @@
 
 namespace blink {
 
-namespace mojom {
-namespace blink {
-enum class PermissionStatus;
-}
-}
-
 // The notification manager, unique to the execution context, is responsible for
 // connecting and communicating with the Mojo notification service.
 //