Redesign the copresence audio handlers.

components/copresence/public/copresence_delegate.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 COMPONENTS_COPRESENCE_PUBLIC_COPRESENCE_DELEGATE_H_
 #define COMPONENTS_COPRESENCE_PUBLIC_COPRESENCE_DELEGATE_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 23 matching lines @@
       const std::string& subscription_id,
       const std::vector<Message>& message) = 0;
 
   virtual net::URLRequestContextGetter* GetRequestContext() const = 0;
 
   virtual const std::string GetPlatformVersionString() const = 0;
 
   virtual const std::string GetAPIKey() const = 0;
 
   virtual WhispernetClient* GetWhispernetClient() = 0;
+
+  virtual ~CopresenceDelegate() {}
 };
 
 }  // namespace copresence
 
 #endif  // COMPONENTS_COPRESENCE_PUBLIC_COPRESENCE_DELEGATE_H_