When the renderer cannot receive data in time, AudioInputSyncWriter stores them so the renderer can receive them later. It has two members for this, std::vector<std::unique_ptr<media::AudioBus>> overflow_buses_ for the audio data, and base::circular_deque<OverflowParams> overflow_params_ for some metadata, see
https://cs.chromium.org/chromium/src/content/browser/renderer_host/media/audio_input_sync_writer.h?l=167. It doesn't really make sense to have two members for this, especially not using different container types :). There's also a bunch of DCHECKs to make sure they don't go out of sync. I'd prefer if there was a struct holding both an AudioBus and the associated metadata, and have a single container holding those.

This may be a good starter bug (of the "set up Goma and figure out Gerrit" size, not the "starter project" size).