Create video and audio decoder threads on demand.

media/filters/ffmpeg_audio_decoder.cc

Index: media/filters/ffmpeg_audio_decoder.cc
diff --git a/media/filters/ffmpeg_audio_decoder.cc b/media/filters/ffmpeg_audio_decoder.cc
index acb0d752fca723572acdc67b4fa33da1abd57222..ad56a875e484e373a28f32956b620ceaad14d1d0 100644
--- a/media/filters/ffmpeg_audio_decoder.cc
+++ b/media/filters/ffmpeg_audio_decoder.cc
@@ -8,6 +8,7 @@
 #include "media/base/audio_decoder_config.h"
 #include "media/base/data_buffer.h"
 #include "media/base/demuxer.h"
+#include "media/base/message_loop_factory.h"

[scherkus (not reviewing), 2012/03/09 20:01:16]

not needed

[tommi (sloooow) - chröme, 2012/03/11 18:49:36]

Done.

 #include "media/base/pipeline.h"
 #include "media/ffmpeg/ffmpeg_common.h"
 
@@ -45,8 +46,10 @@ static bool IsEndOfStream(int result, int decoded_size, Buffer* input) {
 }
 
 
-FFmpegAudioDecoder::FFmpegAudioDecoder(MessageLoop* message_loop)
-    : message_loop_(message_loop),
+FFmpegAudioDecoder::FFmpegAudioDecoder(
+    const base::Callback<MessageLoop*()>& message_loop_cb)
+    : message_loop_cb_(message_loop_cb),
+      message_loop_(NULL),
       codec_context_(NULL),
       bits_per_channel_(0),
       channel_layout_(CHANNEL_LAYOUT_NONE),
@@ -71,8 +74,8 @@ void FFmpegAudioDecoder::Initialize(
     const scoped_refptr<DemuxerStream>& stream,
     const PipelineStatusCB& callback,
     const StatisticsCallback& stats_callback) {
-  message_loop_->PostTask(
-      FROM_HERE,
+  message_loop_ = message_loop_cb_.Run();
+  message_loop_->PostTask(FROM_HERE,

[scherkus (not reviewing), 2012/03/09 20:01:16]

style -- I'd do the following:

message_loop_->PostTask(FROM_HERE, base::Bind(
____&FFmpegAudioDecoder::DoInitialize, ....

[tommi (sloooow) - chröme, 2012/03/11 18:49:36]

Done.

       base::Bind(&FFmpegAudioDecoder::DoInitialize, this,
                  stream, callback, stats_callback));
 }
@@ -80,8 +83,8 @@ void FFmpegAudioDecoder::Initialize(
 void FFmpegAudioDecoder::Read(const ReadCB& callback) {
   // Complete operation asynchronously on different stack of execution as per
   // the API contract of AudioDecoder::Read()
-  message_loop_->PostTask(FROM_HERE, base::Bind(
-      &FFmpegAudioDecoder::DoRead, this, callback));
+  message_loop_->PostTask(FROM_HERE,

[scherkus (not reviewing), 2012/03/09 20:01:16]

ditto here + below (i.e., revert these edits)

[tommi (sloooow) - chröme, 2012/03/11 18:49:36]

Done.

+      base::Bind(&FFmpegAudioDecoder::DoRead, this, callback));
 }
 
 int FFmpegAudioDecoder::bits_per_channel() {
@@ -97,8 +100,8 @@ int FFmpegAudioDecoder::samples_per_second() {
 }
 
 void FFmpegAudioDecoder::Reset(const base::Closure& closure) {
-  message_loop_->PostTask(FROM_HERE, base::Bind(
-      &FFmpegAudioDecoder::DoReset, this, closure));
+  message_loop_->PostTask(FROM_HERE,
+      base::Bind(&FFmpegAudioDecoder::DoReset, this, closure));
 }
 
 void FFmpegAudioDecoder::DoInitialize(
@@ -249,8 +252,8 @@ void FFmpegAudioDecoder::ReadFromDemuxerStream() {
 void FFmpegAudioDecoder::DecodeBuffer(const scoped_refptr<Buffer>& buffer) {
   // TODO(scherkus): fix FFmpegDemuxerStream::Read() to not execute our read
   // callback on the same execution stack so we can get rid of forced task post.
-  message_loop_->PostTask(FROM_HERE, base::Bind(
-      &FFmpegAudioDecoder::DoDecodeBuffer, this, buffer));
+  message_loop_->PostTask(FROM_HERE,
+      base::Bind(&FFmpegAudioDecoder::DoDecodeBuffer, this, buffer));
 }
 
 void FFmpegAudioDecoder::UpdateDurationAndTimestamp(