Fix the crash due to AudioRendererImpl::audio_clock_ being null

media/renderers/audio_renderer_impl.cc

Index: media/renderers/audio_renderer_impl.cc
diff --git a/media/renderers/audio_renderer_impl.cc b/media/renderers/audio_renderer_impl.cc
index 25f4ef34d83c294bfddd2ee7543e81672291036f..e1ca2c180019981e552671922c43b00b980ff224 100644
--- a/media/renderers/audio_renderer_impl.cc
+++ b/media/renderers/audio_renderer_impl.cc
@@ -337,21 +337,21 @@ void AudioRendererImpl::Initialize(DemuxerStream* stream,
   DCHECK(stream);
   DCHECK_EQ(stream->type(), DemuxerStream::AUDIO);
   DCHECK(!init_cb.is_null());
+
+  base::AutoLock auto_lock(lock_);
   DCHECK(state_ == kUninitialized || state_ == kFlushed);
   DCHECK(sink_.get());
 
   // If we are re-initializing playback (e.g. switching media tracks), stop the
   // sink first.
   if (state_ == kFlushed) {
-    sink_->Stop();
-    audio_clock_.reset();
+    // Release the lock while we are stopping the sink to avoid deadlock if the
+    // sink needs to wait for the current Render to finish.
+    auto* sink = sink_.get();
+    base::AutoUnlock auto_unlock(lock_);
+    sink->Stop();
   }
 
-  // Trying to track down AudioClock crash, http://crbug.com/674856.
-  // AudioRenderImpl should only be initialized once to avoid destroying
-  // AudioClock while the audio thread is still using it.
-  CHECK_EQ(audio_clock_.get(), nullptr);
-
   state_ = kInitializing;
   client_ = client;