Remove reference counting from media::VideoDecoder and friends.

media/filters/decrypting_video_decoder.cc

Index: media/filters/decrypting_video_decoder.cc
diff --git a/media/filters/decrypting_video_decoder.cc b/media/filters/decrypting_video_decoder.cc
index 6fe6e69e0fd3304eea6008568917426f0bb71956..6179fd72369a002cc0ab38d8fcf97404fc0a40b2 100644
--- a/media/filters/decrypting_video_decoder.cc
+++ b/media/filters/decrypting_video_decoder.cc
@@ -24,6 +24,7 @@ DecryptingVideoDecoder::DecryptingVideoDecoder(
     const scoped_refptr<base::MessageLoopProxy>& message_loop,
     const SetDecryptorReadyCB& set_decryptor_ready_cb)
     : message_loop_(message_loop),
+      weak_factory_(this),
       state_(kUninitialized),
       set_decryptor_ready_cb_(set_decryptor_ready_cb),
       decryptor_(NULL),
@@ -40,6 +41,7 @@ void DecryptingVideoDecoder::Initialize(
   DCHECK_EQ(state_, kUninitialized) << state_;
   DCHECK(stream);
   init_cb_ = BindToCurrentLoop(status_cb);
+  weak_this_ = weak_factory_.GetWeakPtr();

[Ami GONE FROM CHROMIUM, 2013/03/22 23:48:01]

Nothing ever invalidates the underlying WeakReference.
You should call weak_factory_.InvalidateWeakPtrs() in the dtor of each class in
this CL that uses this idiom.

[xhwang, 2013/03/22 23:59:03]

Hmm, is this required for all classes that uses WeakPtrFactory? Looks like
WeakPtrFactory owns internal::WeakReferenceOwner, whose dtor calls Invalidate
automatically.

[1]
https://code.google.com/p/chromium/codesearch#chromium/src/base/memory/weak_p...

[2]
https://code.google.com/p/chromium/codesearch#chromium/src/base/memory/weak_p...

[Ami GONE FROM CHROMIUM, 2013/03/23 00:02:01]

Oh good, I think you're right!
(this is how I _thought_ it worked, but then when I looked today I missed this,
visually replacing WeakReferenceOwner with WeakReference).

 
   const VideoDecoderConfig& config = stream->video_decoder_config();
   if (!config.IsValidConfig()) {
@@ -61,7 +63,7 @@ void DecryptingVideoDecoder::Initialize(
 
   state_ = kDecryptorRequested;
   set_decryptor_ready_cb_.Run(BindToCurrentLoop(base::Bind(
-      &DecryptingVideoDecoder::SetDecryptor, this)));
+      &DecryptingVideoDecoder::SetDecryptor, weak_this_)));
 }
 
 void DecryptingVideoDecoder::Read(const ReadCB& read_cb) {
@@ -166,7 +168,7 @@ void DecryptingVideoDecoder::SetDecryptor(Decryptor* decryptor) {
   state_ = kPendingDecoderInit;
   decryptor_->InitializeVideoDecoder(
       demuxer_stream_->video_decoder_config(), BindToCurrentLoop(base::Bind(
-          &DecryptingVideoDecoder::FinishInitialization, this)));
+          &DecryptingVideoDecoder::FinishInitialization, weak_this_)));
 }
 
 void DecryptingVideoDecoder::FinishInitialization(bool success) {
@@ -188,7 +190,7 @@ void DecryptingVideoDecoder::FinishInitialization(bool success) {
   }
 
   decryptor_->RegisterNewKeyCB(Decryptor::kVideo, BindToCurrentLoop(
-      base::Bind(&DecryptingVideoDecoder::OnKeyAdded, this)));
+      base::Bind(&DecryptingVideoDecoder::OnKeyAdded, weak_this_)));
 
   // Success!
   state_ = kIdle;
@@ -230,7 +232,7 @@ void DecryptingVideoDecoder::ReadFromDemuxerStream() {
   DCHECK(!read_cb_.is_null());
 
   demuxer_stream_->Read(
-      base::Bind(&DecryptingVideoDecoder::DecryptAndDecodeBuffer, this));
+      base::Bind(&DecryptingVideoDecoder::DecryptAndDecodeBuffer, weak_this_));

[Ami GONE FROM CHROMIUM, 2013/03/22 23:48:01]

What guarantees you get called back on this thread?  (which is required for
reading weak_this_ to be legit).
IOW do you want s/Bind/BindToCurrentLoop/?

[scherkus (not reviewing), 2013/03/28 02:00:01]

short term: it's part of the API contract to call back async-ly and on the
calling thread

medium term: xhwang is in the midst of having video decoders not make async
calls to demuxers, so this code will go away

 }
 
 void DecryptingVideoDecoder::DecryptAndDecodeBuffer(
@@ -253,7 +255,7 @@ void DecryptingVideoDecoder::DecryptAndDecodeBuffer(
     decryptor_->DeinitializeDecoder(Decryptor::kVideo);
     decryptor_->InitializeVideoDecoder(
         demuxer_stream_->video_decoder_config(), BindToCurrentLoop(base::Bind(
-            &DecryptingVideoDecoder::FinishConfigChange, this)));
+            &DecryptingVideoDecoder::FinishConfigChange, weak_this_)));
     return;
   }
 
@@ -289,7 +291,7 @@ void DecryptingVideoDecoder::DecodePendingBuffer() {
 
   decryptor_->DecryptAndDecodeVideo(
       pending_buffer_to_decode_, BindToCurrentLoop(base::Bind(
-          &DecryptingVideoDecoder::DeliverFrame, this, buffer_size)));
+          &DecryptingVideoDecoder::DeliverFrame, weak_this_, buffer_size)));
 }
 
 void DecryptingVideoDecoder::DeliverFrame(