Fix crash in VideoRendererBase::ThreadMain().

media/filters/video_renderer_base.cc

Index: media/filters/video_renderer_base.cc
diff --git a/media/filters/video_renderer_base.cc b/media/filters/video_renderer_base.cc
index 37a24edd7b1fb6890baa7eeb8119f64c6faafb21..2078751e3081d538d2cb58c0a3091d8969cf5408 100644
--- a/media/filters/video_renderer_base.cc
+++ b/media/filters/video_renderer_base.cc
@@ -45,7 +45,7 @@ VideoRendererBase::VideoRendererBase(
 
 VideoRendererBase::~VideoRendererBase() {
   base::AutoLock auto_lock(lock_);
-  CHECK(state_ == kUninitialized || state_ == kStopped) << state_;
+  CHECK_EQ(state_, kStopped);

[acolwell GONE FROM CHROMIUM, 2013/02/20 17:01:14]

Won't this crash if an error is encountered before the renderer is initialized.
For example, wouldn't a demuxer init error cause this to be destroyed in the
kUninitialized state w/o Stop() being called? Audio-only playback might be
another case.

[scherkus (not reviewing), 2013/02/21 20:43:54]

Indeed it will!

   CHECK_EQ(thread_, base::kNullThreadHandle);
 }
 
@@ -92,7 +92,7 @@ void VideoRendererBase::ResetDecoder() {
 void VideoRendererBase::Stop(const base::Closure& callback) {
   DCHECK(message_loop_->BelongsToCurrentThread());
   base::AutoLock auto_lock(lock_);
-  if (state_ == kUninitialized || state_ == kStopped) {
+  if (state_ == kStopped) {

[scherkus (not reviewing), 2013/02/20 08:26:11]

note: state == kUninitialized actually runs the Stop() code path now (hence the
check for decoder_ below)

[acolwell GONE FROM CHROMIUM, 2013/02/20 17:01:14]

This seems a little weird. Shouldn't we transition to a kInitializing state
inside Initialize() somewhere? That seems to make a little more sense then
letting kUninitialized fall through here. It avoids the "If we are
uninitialized, why do we have to clean up state." train of thought when looking
at this code.

[scherkus (not reviewing), 2013/02/21 20:43:54]

Yeah that was on my mind. I fully admit that I was a bit rushed to get something
together before the flight attendant chastised me.

     callback.Run();
     return;
   }
@@ -126,7 +126,12 @@ void VideoRendererBase::Stop(const base::Closure& callback) {
     return;
   }
 
-  decoder_->Stop(callback);
+  if (decoder_) {
+    decoder_->Stop(callback);
+    return;
+  }
+
+  callback.Run();
 }
 
 void VideoRendererBase::StopDecoder(const base::Closure& callback) {
@@ -527,6 +532,9 @@ void VideoRendererBase::AttemptRead_Locked() {
 
 void VideoRendererBase::OnDecoderResetDone() {
   base::AutoLock auto_lock(lock_);
+  if (state_ == kStopped)
+    return;
+
   DCHECK_EQ(kFlushingDecoder, state_);
   DCHECK(!pending_read_);