Create video and audio decoder threads on demand.

media/filters/ffmpeg_decoder_unittest.h

Index: media/filters/ffmpeg_decoder_unittest.h
diff --git a/media/filters/ffmpeg_decoder_unittest.h b/media/filters/ffmpeg_decoder_unittest.h
new file mode 100644
index 0000000000000000000000000000000000000000..e558c30b4530d1c6d0d94916ffb6b487dd5c03ef
--- /dev/null
+++ b/media/filters/ffmpeg_decoder_unittest.h
@@ -0,0 +1,13 @@
+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef MEDIA_FILTERS_FFMPEG_DECODER_UNITTEST_H_
+#define MEDIA_FILTERS_FFMPEG_DECODER_UNITTEST_H_
+
+namespace media {
+// Used to inject our message loop into the FFmpeg[Audio|Video|Decoder.
+template<class T> T Identity(T t) { return t; }

[Ami GONE FROM CHROMIUM, 2012/03/11 23:43:12]

I think you misunderstood my comment about namespace/static.
My point was that instead of using an anonymous namespace:

namespace {
template<class T> T Identity(T t) { return t; }
}

media code makes such things file-static:
template<class T> static T Identity(T t) { return t; }

, not that you should move it into the media namespace (or need a new .h).
This function is simple enough that duplicating its code in two test.cc files
seems fine to me.

+}  // namespace media
+
+#endif  // MEDIA_FILTERS_FFMPEG_DECODER_UNITTEST_H_