media: Renderer::Flush now accepting OnceClosure.

No users of flush used or required a repeating closure, so
switching to base::OnceClosure.

Bug: 1007799, 1007810
Change-Id: I675f2a5251360a40b13e509ec7daa1dbdcccaa28
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1878554
Reviewed-by: Kenneth MacKay <kmackay@chromium.org>
Reviewed-by: Xiaohan Wang <xhwang@chromium.org>
Commit-Queue: Chris Mumford <cmumford@google.com>
Cr-Commit-Position: refs/heads/master@{#709583}

diff --git a/media/renderers/renderer_impl.h b/media/renderers/renderer_impl.h
index 379be97..5b1e0664 100644
--- a/media/renderers/renderer_impl.h
+++ b/media/renderers/renderer_impl.h

@@ -58,7 +58,7 @@
                   const PipelineStatusCB& init_cb) final;
   void SetCdm(CdmContext* cdm_context,
               const CdmAttachedCB& cdm_attached_cb) final;
-  void Flush(const base::Closure& flush_cb) final;
+  void Flush(base::OnceClosure flush_cb) final;
   void StartPlayingFrom(base::TimeDelta time) final;
   void SetPlaybackRate(double playback_rate) final;
   void SetVolume(float volume) final;
@@ -209,7 +209,7 @@
 
   // Temporary callback used for Initialize() and Flush().
   PipelineStatusCB init_cb_;
-  base::Closure flush_cb_;
+  base::OnceClosure flush_cb_;
 
   std::unique_ptr<RendererClientInternal> audio_renderer_client_;
   std::unique_ptr<RendererClientInternal> video_renderer_client_;