Makes RenderFrameObserver/RenderViewObserver::OnDestruct pure virtual.

chromecast/renderer/cast_media_load_deferrer.cc

 // 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 "chromecast/renderer/cast_media_load_deferrer.h"
 
 #include "base/callback_helpers.h"
 #include "base/logging.h"
 
 namespace chromecast {
 
 CastMediaLoadDeferrer::CastMediaLoadDeferrer(
     content::RenderFrame* render_frame,
     const base::Closure& continue_loading_cb)
     : content::RenderFrameObserver(render_frame),
       continue_loading_cb_(continue_loading_cb) {
   DCHECK(!continue_loading_cb_.is_null());
 }
 
 CastMediaLoadDeferrer::~CastMediaLoadDeferrer() {}
 
 void CastMediaLoadDeferrer::WasShown() {
   continue_loading_cb_.Run();
   delete this;
 }
 
+void CastMediaLoadDeferrer::OnDestruct() {
+  delete this;
+}
+
 }  // namespace chromecast