Remove pure-virtual MediaStreamProvider::Unregister method and make overrides non-virtual.

content/browser/renderer_host/media/audio_input_device_manager.h

Index: content/browser/renderer_host/media/audio_input_device_manager.h
diff --git a/content/browser/renderer_host/media/audio_input_device_manager.h b/content/browser/renderer_host/media/audio_input_device_manager.h
index a2d4ca4f92c64c755ea65c0d7c820be2acdccd70..b123ce482f5af4864964a3f95edbcfb9852e307d 100644
--- a/content/browser/renderer_host/media/audio_input_device_manager.h
+++ b/content/browser/renderer_host/media/audio_input_device_manager.h
@@ -44,11 +44,12 @@ class CONTENT_EXPORT AudioInputDeviceManager : public MediaStreamProvider {
   // is not opened, otherwise the opened device. Called on IO thread.
   const StreamDeviceInfo* GetOpenedDeviceInfoById(int session_id);
 
+  void Unregister();
+
   // MediaStreamProvider implementation, called on IO thread.
   void Register(MediaStreamProviderListener* listener,
                 const scoped_refptr<base::SingleThreadTaskRunner>&
                     device_task_runner) override;
-  void Unregister() override;
   void EnumerateDevices(MediaStreamType stream_type) override;
   int Open(const StreamDeviceInfo& device) override;
   void Close(int session_id) override;