Use PlaybackHasEnded generically to stop double ended event firing

Wez pointed out a good issue in crrev.com/c/1153144

Bug: 867872
Change-Id: I40e6f100c1f2fdee77ff536923e202f18d4eb7a1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2212932Reviewed-by: Wez <wez@chromium.org>
Commit-Queue: Ted Meyer <tmathmeyer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#771615}

media/renderers/renderer_impl.cc

@@ -853,19 +853,15 @@ void RendererImpl::OnRendererEnded(DemuxerStream::Type type) {
   DCHECK((type == DemuxerStream::AUDIO) || (type == DemuxerStream::VIDEO));
   TRACE_EVENT1("media", "RendererImpl::OnRendererEnded", "type", type_string);
 
-  if (state_ != STATE_PLAYING)
+  // If all streams are ended, do not propagate a redundant ended event.
+  if (state_ != STATE_PLAYING || PlaybackHasEnded())
     return;
 
   if (type == DemuxerStream::AUDIO) {
-    // If all streams are ended, do not propagate a redundant ended event.
-    if (audio_ended_ && PlaybackHasEnded())
-      return;
+    DCHECK(audio_renderer_);
     audio_ended_ = true;
   } else {
     DCHECK(video_renderer_);
-    // If all streams are ended, do not propagate a redundant ended event.
-    if (audio_ended_ && PlaybackHasEnded())
-      return;
     video_ended_ = true;
     video_renderer_->OnTimeStopped();
   }