PushRegistration.unregister() can fail with a NetworkError.

Source/modules/push_messaging/PushError.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 #include "modules/push_messaging/PushError.h"
 
 #include "core/dom/ExceptionCode.h"
 #include "wtf/OwnPtr.h"
 
 namespace blink {
 
 PassRefPtrWillBeRawPtr<DOMException> PushError::take(ScriptPromiseResolver*, WebType* webErrorRaw)
 {
     OwnPtr<WebType> webError = adoptPtr(webErrorRaw);
     switch (webError->errorType) {
     case WebPushError::ErrorTypeAbort:
         return DOMException::create(AbortError, webError->message);
+    case WebPushError::ErrorTypeNetwork:
+        return DOMException::create(NetworkError, webError->message);
     case WebPushError::ErrorTypeNotFound:
         return DOMException::create(NotFoundError, webError->message);
     case WebPushError::ErrorTypeUnknown:
         return DOMException::create(UnknownError);
     }
     ASSERT_NOT_REACHED();
     return DOMException::create(UnknownError);
 }
 
 void PushError::dispose(WebType* webErrorRaw)
 {
     delete webErrorRaw;
 }
 
 } // namespace blink