Makes RenderFrameObserver/RenderViewObserver::OnDestruct pure virtual.

content/renderer/media/midi_dispatcher.cc

 // Copyright 2013 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 "content/renderer/media/midi_dispatcher.h"
 
 #include "base/bind.h"
 #include "content/public/common/service_registry.h"
 #include "content/public/renderer/render_frame.h"
 #include "third_party/WebKit/public/platform/WebSecurityOrigin.h"
 #include "third_party/WebKit/public/platform/WebString.h"
 #include "third_party/WebKit/public/web/modules/webmidi/WebMIDIOptions.h"
 #include "third_party/WebKit/public/web/modules/webmidi/WebMIDIPermissionRequest.h"
 
 using blink::WebMIDIPermissionRequest;
 using blink::WebMIDIOptions;
 using blink::WebSecurityOrigin;
 
 namespace content {
 
 MidiDispatcher::MidiDispatcher(RenderFrame* render_frame)
     : RenderFrameObserver(render_frame) {
 }
 
 MidiDispatcher::~MidiDispatcher() {}
 
+void MidiDispatcher::OnDestruct() {
+  delete this;
+}
+
 void MidiDispatcher::requestPermission(const WebMIDIPermissionRequest& request,
                                        const WebMIDIOptions& options) {
   if (!permission_service_.get()) {
     render_frame()->GetServiceRegistry()->ConnectToRemoteService(
         mojo::GetProxy(&permission_service_));
   }
 
   int permission_request_id =
       requests_.Add(new WebMIDIPermissionRequest(request));
 
@@ skipping 23 matching lines @@
                                      blink::mojom::PermissionStatus status) {
   // |request| can be NULL when the request is canceled.
   WebMIDIPermissionRequest* request = requests_.Lookup(request_id);
   if (!request)
     return;
   request->setIsAllowed(status == blink::mojom::PermissionStatus::GRANTED);
   requests_.Remove(request_id);
 }
 
 }  // namespace content