Convert some audio code to OnceCallback.

content/browser/renderer_host/media/audio_renderer_host_unittest.cc

Index: content/browser/renderer_host/media/audio_renderer_host_unittest.cc
diff --git a/content/browser/renderer_host/media/audio_renderer_host_unittest.cc b/content/browser/renderer_host/media/audio_renderer_host_unittest.cc
index 20ea45557eb243a36ef6ec40955a899fecfa02bd..cecde664165cf2b912341acb9954bd95890686bf 100644
--- a/content/browser/renderer_host/media/audio_renderer_host_unittest.cc
+++ b/content/browser/renderer_host/media/audio_renderer_host_unittest.cc
@@ -57,11 +57,11 @@ const char kInvalidDeviceId[] = "invalid-device-id";
 
 void ValidateRenderFrameId(int render_process_id,
                            int render_frame_id,
-                           const base::Callback<void(bool)>& callback) {
+                           base::OnceCallback<void(bool)> callback) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   const bool frame_exists = (render_frame_id == kRenderFrameId);
   BrowserThread::PostTask(BrowserThread::IO, FROM_HERE,
-                          base::Bind(callback, frame_exists));
+                          base::BindOnce(std::move(callback), frame_exists));
 }