Implement WebPushProvider.unregister() in Chromium.

content/public/browser/push_messaging_service.h

Index: content/public/browser/push_messaging_service.h
diff --git a/content/public/browser/push_messaging_service.h b/content/public/browser/push_messaging_service.h
index fdc92f432d49789e98dab1c6136fc5e6e84a029a..624efb11a0cf08a20fc745f0d9a96c5bc56daf6c 100644
--- a/content/public/browser/push_messaging_service.h
+++ b/content/public/browser/push_messaging_service.h
@@ -19,9 +19,10 @@ namespace content {
 // push messaging services like GCM. Must only be used on the UI thread.
 class CONTENT_EXPORT PushMessagingService {
  public:
-  typedef base::Callback<void(const std::string& /* registration_id */,
-                              PushRegistrationStatus /* status */)>
-      RegisterCallback;
+  using RegisterCallback =
+      base::Callback<void(const std::string& /* registration_id */,
+                          PushRegistrationStatus /* status */)>;
+  using UnregisterCallback = base::Callback<void(PushUnregistrationStatus)>;
 
   virtual ~PushMessagingService() {}
 
@@ -49,6 +50,12 @@ class CONTENT_EXPORT PushMessagingService {
                                   const std::string& sender_id,
                                   const RegisterCallback& callback) = 0;
 
+  // Unregister an origin and its associated service worker registration id from
+  // the push service.
+  virtual void Unregister(const GURL& requesting_origin,
+                          int64 service_worker_registration_id,
+                          const UnregisterCallback& callback) = 0;
+
   // Check whether the requester has permission to register for Push
   // Messages
   // TODO(mvanouwerkerk): Delete once the Push API flows through platform.