media: Add kError to DemuxerStream::Status

Some DemuxerStream could hit non-recoverable fatal errors. For example,
DecryptingDemuxerStream cannot decrypt a buffer because the CDM was
crashed.

This CL adds a new kError status to DemuxerStream::Status to indicate
such conditions.

BUG=730766
TEST=New unittests added.

Cq-Include-Trybots: master.tryserver.chromium.android:android_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel
Change-Id: Ia07e14662d7da852f712076dcc94aed1900aaba3
Reviewed-on: https://chromium-review.googlesource.com/598702
Commit-Queue: Xiaohan Wang <xhwang@chromium.org>
Reviewed-by: Matthew Wolenetz <wolenetz@chromium.org>
Reviewed-by: Yuri Wiitala <miu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#491960}

diff --git a/media/filters/decrypting_audio_decoder_unittest.cc b/media/filters/decrypting_audio_decoder_unittest.cc
index fb34c76..b8bca93b1b 100644
--- a/media/filters/decrypting_audio_decoder_unittest.cc
+++ b/media/filters/decrypting_audio_decoder_unittest.cc

@@ -202,6 +202,7 @@
     decoder_->Decode(encrypted_buffer_,
                      base::Bind(&DecryptingAudioDecoderTest::DecodeDone,
                                 base::Unretained(this)));
+
     base::RunLoop().RunUntilIdle();
   }