After https://codereview.chromium.org/1996453003 is submitted, we need to add timestamp parameter in PpapiPluginMsg_VideoEncoder_BitstreamBufferReady().
https://code.google.com/p/chromium/codesearch#chromium/src/content/renderer/pepper/pepper_video_encoder_host.cc&q=PepperVideoEncoderHost::BitstreamBufferReady&sq=package:chromium&type=cs&l=450