decrypting_{audio,video}_decoder_unittest.cc: Remove dead code.

media/filters/decrypting_audio_decoder_unittest.cc

Index: media/filters/decrypting_audio_decoder_unittest.cc
diff --git a/media/filters/decrypting_audio_decoder_unittest.cc b/media/filters/decrypting_audio_decoder_unittest.cc
index 94d388bbf90c21759a8368f06864596efc2a01fd..70166bf77f5ada41abae4b23f4d956d0101e6a57 100644
--- a/media/filters/decrypting_audio_decoder_unittest.cc
+++ b/media/filters/decrypting_audio_decoder_unittest.cc
@@ -52,16 +52,6 @@ static scoped_refptr<DecoderBuffer> CreateFakeEncryptedBuffer() {
   return buffer;
 }
 
-// Use anonymous namespace here to prevent the actions to be defined multiple
-// times across multiple test files. Sadly we can't use static for them.
-namespace {
-
-ACTION_P(ReturnBuffer, buffer) {
-  return buffer;
-}
-
-}  // namespace
-
 class DecryptingAudioDecoderTest : public testing::Test {
  public:
   DecryptingAudioDecoderTest()