Add native file picker impl using SelectFileDialog.

chrome/browser/intents/intent_service_host.h

 // Copyright (c) 2012 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 CHROME_BROWSER_INTENTS_INTENT_SERVICE_HOST_H_
 #define CHROME_BROWSER_INTENTS_INTENT_SERVICE_HOST_H_
 
 class GURL;
 
 namespace content {
 class WebIntentsDispatcher;
 }
 
 namespace web_intents {
 
 // Interface allowing services to be implemented in various host environments.
+// Implementations should be owned by their creator.
 class IntentServiceHost {
  public:
   virtual ~IntentServiceHost() {}
 
   // Handle all necessary service-side processing of an intent.
   virtual void HandleIntent(content::WebIntentsDispatcher* dispatcher) = 0;
 };
 
 }  // web_intents namespaces
 
 #endif  // CHROME_BROWSER_INTENTS_INTENT_SERVICE_HOST_H_