Implement WebPushProvider.unregister() in Chromium.

content/public/common/push_messaging_status.h

Index: content/public/common/push_messaging_status.h
diff --git a/content/public/common/push_messaging_status.h b/content/public/common/push_messaging_status.h
index 5469c9eabfbb62df5e9eb958d5b31e8d23ed1fa3..2351b5114097ac7de71e3e61f47694dc19c014d5 100644
--- a/content/public/common/push_messaging_status.h
+++ b/content/public/common/push_messaging_status.h
@@ -51,6 +51,21 @@ enum PushRegistrationStatus {
   PUSH_REGISTRATION_STATUS_LAST = PUSH_REGISTRATION_STATUS_SUCCESS_FROM_CACHE
 };
 
+// Push unregistration success / error codes for internal use & reporting.
+enum PushUnregistrationStatus {
+  // The unregistration was successful.
+  PUSH_UNREGISTRATION_STATUS_SUCCESS_UNREGISTER,
+
+  // The registration was not registered.
+  PUSH_UNREGISTRATION_STATUS_SUCCESS_WAS_NOT_REGISTERED,
+
+  // The unregistration did not happen because of a network error.
+  PUSH_UNREGISTRATION_STATUS_NETWORK_ERROR,
+
+  // The unregistration did not happen because of a miscellaneous error.
+  PUSH_UNREGISTRATION_STATUS_UNKNOWN_ERROR,
+};
+
 // Push get registration success / error codes for internal use.
 enum PushGetRegistrationStatus {
   // Getting the registration was successful.