Added MediaSourceState unit test.

media/filters/decrypting_demuxer_stream_unittest.cc

Index: media/filters/decrypting_demuxer_stream_unittest.cc
diff --git a/media/filters/decrypting_demuxer_stream_unittest.cc b/media/filters/decrypting_demuxer_stream_unittest.cc
index 36e5d0e9e4ddc6dda6de378f1aae1ac2083ac88f..d13aec42f0a17f8bb10df53acae7d9f06833b123 100644
--- a/media/filters/decrypting_demuxer_stream_unittest.cc
+++ b/media/filters/decrypting_demuxer_stream_unittest.cc
@@ -55,10 +55,6 @@ ACTION_P(ReturnBuffer, buffer) {
   arg0.Run(buffer.get() ? DemuxerStream::kOk : DemuxerStream::kAborted, buffer);
 }
 
-MATCHER(IsEndOfStream, "end of stream") {
-  return arg->end_of_stream();
-}
-
 }  // namespace
 
 class DecryptingDemuxerStreamTest : public testing::Test {