WebPushClient requires a virtual destructor.

public/platform/WebPushClient.h

 // 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.
 
 #ifndef WebPushClient_h
 #define WebPushClient_h
 
 #include "public/platform/WebCallbacks.h"
 #include "public/platform/WebPushError.h"
 #include "public/platform/WebString.h"
 
 namespace blink {
 
 struct WebPushRegistration;
 
 typedef WebCallbacks<WebPushRegistration, WebPushError> WebPushRegistrationCallbacks;
 
 class WebPushClient {
 public:
+    virtual ~WebPushClient() { }
     virtual void registerPushMessaging(const WebString& senderId, WebPushRegistrationCallbacks*) = 0;
 };
 
 } // namespace blink
 
 #endif // WebPushClient_h