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 cd6383018a61348a9dadaca6bca336766c076cc7..93dfbfb93881e340b5a4a6d155521f6a826dffb3 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;
     }
   }