Add DecryptingAudioDecoder.

media/filters/decrypting_video_decoder_unittest.cc

Index: media/filters/decrypting_video_decoder_unittest.cc
diff --git a/media/filters/decrypting_video_decoder_unittest.cc b/media/filters/decrypting_video_decoder_unittest.cc
index 4e8970f317c55a5eb9abae204f3ad7e13abbec60..fcdf5de34e6452d51a5f5db7a8f9d25a9a173018 100644
--- a/media/filters/decrypting_video_decoder_unittest.cc
+++ b/media/filters/decrypting_video_decoder_unittest.cc
@@ -47,6 +47,10 @@ 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) {
   arg0.Run(buffer ? DemuxerStream::kOk : DemuxerStream::kAborted, buffer);
 }
@@ -76,6 +80,8 @@ MATCHER(IsNullCallback, "") {
   return (arg.is_null());
 }
 
+}  // namespace
+
 class DecryptingVideoDecoderTest : public testing::Test {
  public:
   DecryptingVideoDecoderTest()