Fix a few races due to lack of locking in AudioRendererImpl::FillBuffer().

Also switched to using kNoTimestamp() to represent uninitialized timestamps.

TBR=timurrrr
BUG=109875,112418,122447
TEST=tsan is happy, also run http://mastodon.sea/demos/crbug122447

Review URL: https://chromiumcodereview.appspot.com/10355006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@135213 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 20 insertions, 16 deletions

diff --git a/media/filters/audio_renderer_impl.cc b/media/filters/audio_renderer_impl.cc
index ddb2d287..3821093 100644
--- a/media/filters/audio_renderer_impl.cc
+++ b/media/filters/audio_renderer_impl.cc
@@ -20,6 +20,7 @@ AudioRendererImpl::AudioRendererImpl(media::AudioRendererSink* sink)
       pending_read_(false),
       received_end_of_stream_(false),
       rendered_end_of_stream_(false),
+      audio_time_buffered_(kNoTimestamp()),
       bytes_per_frame_(0),
       bytes_per_second_(0),
       stopped_(false),
@@ -119,7 +120,7 @@ void AudioRendererImpl::Seek(base::TimeDelta time, const PipelineStatusCB& cb) {
   seek_timestamp_ = time;
 
   // Throw away everything and schedule our reads.
-  audio_time_buffered_ = base::TimeDelta();
+  audio_time_buffered_ = kNoTimestamp();
   received_end_of_stream_ = false;
   rendered_end_of_stream_ = false;
 
@@ -377,11 +378,8 @@ int AudioRendererImpl::Render(const std::vector<float*>& audio_data,
 uint32 AudioRendererImpl::FillBuffer(uint8* dest,
                                      uint32 requested_frames,
                                      const base::TimeDelta& playback_delay) {
-  // The |audio_time_buffered_| is the ending timestamp of the last frame
-  // buffered at the audio device. |playback_delay| is the amount of time
-  // buffered at the audio device. The current time can be computed by their
-  // difference.
-  base::TimeDelta current_time = audio_time_buffered_ - playback_delay;
+  base::TimeDelta current_time = kNoTimestamp();
+  base::TimeDelta max_time = kNoTimestamp();
 
   size_t frames_written = 0;
   base::Closure underflow_cb;
@@ -432,17 +430,24 @@ uint32 AudioRendererImpl::FillBuffer(uint8* dest,
       // Otherwise fill the buffer.
       frames_written = algorithm_->FillBuffer(dest, requested_frames);
     }
-  }
 
-  base::TimeDelta previous_time_buffered = audio_time_buffered_;
-  // The call to FillBuffer() on |algorithm_| has increased the amount of
-  // buffered audio data. Update the new amount of time buffered.
-  audio_time_buffered_ = algorithm_->GetTime();
+    // The |audio_time_buffered_| is the ending timestamp of the last frame
+    // buffered at the audio device. |playback_delay| is the amount of time
+    // buffered at the audio device. The current time can be computed by their
+    // difference.
+    if (audio_time_buffered_ != kNoTimestamp()) {
+      current_time = audio_time_buffered_ - playback_delay;
+    }
+
+    // The call to FillBuffer() on |algorithm_| has increased the amount of
+    // buffered audio data. Update the new amount of time buffered.
+    max_time = audio_time_buffered_ = algorithm_->GetTime();
+  }
 
-  if (previous_time_buffered.InMicroseconds() > 0 &&
-      (previous_time_buffered != audio_time_buffered_ ||
-       current_time > host()->GetTime())) {
-    time_cb_.Run(current_time, audio_time_buffered_);
+  if (current_time != kNoTimestamp() &&
+      current_time > host()->GetTime() &&
+      max_time != kNoTimestamp()) {
+    time_cb_.Run(current_time, max_time);
   }
 
   if (!underflow_cb.is_null())
diff --git a/media/filters/audio_renderer_impl.h b/media/filters/audio_renderer_impl.h
index e39f75b..8897bc6 100644
--- a/media/filters/audio_renderer_impl.h
+++ b/media/filters/audio_renderer_impl.h
@@ -156,7 +156,6 @@ class MEDIA_EXPORT AudioRendererImpl
   bool rendered_end_of_stream_;
 
   // The timestamp of the last frame (i.e. furthest in the future) buffered.
-  // TODO(ralphl): Update this value after seeking.
   base::TimeDelta audio_time_buffered_;
 
   // Filter callbacks.