Add a media pipeline status error code for decryption error.

media/filters/ffmpeg_video_decoder.cc

Index: media/filters/ffmpeg_video_decoder.cc
diff --git a/media/filters/ffmpeg_video_decoder.cc b/media/filters/ffmpeg_video_decoder.cc
index 4e76c0d415ad41a264e63c40299dc39c268ff92a..a2dcfde48c6f065f2169df4c856e9e07c3b4577a 100644
--- a/media/filters/ffmpeg_video_decoder.cc
+++ b/media/filters/ffmpeg_video_decoder.cc
@@ -286,11 +286,10 @@ void FFmpegVideoDecoder::DoDecodeBuffer(const scoped_refptr<Buffer>& buffer) {
   scoped_refptr<Buffer> unencrypted_buffer = buffer;
   if (buffer->GetDecryptConfig() && buffer->GetDataSize()) {
     unencrypted_buffer = decryptor_.Decrypt(buffer);
-    // TODO(xhwang): Add a decryption error code, see http://crbug.com/121177
     if (!unencrypted_buffer || !unencrypted_buffer->GetDataSize()) {
       state_ = kDecodeFinished;
       DeliverFrame(VideoFrame::CreateEmptyFrame());
-      host()->SetError(PIPELINE_ERROR_DECODE);
+      host()->SetError(PIPELINE_ERROR_DECRYPT);
       return;
     }
   }