Merge "Discard invisible surfaces"

  ATRACE_NAME("DisplaySurface::OnPostConsumer");

  std::lock_guard<std::mutex> autolock(lock_);

  if (!IsVisible()) {

    ALOGD_IF(TRACE,

             "DisplaySurface::OnPostConsumer: Discarding buffer_id=%d on "

             "invisible surface.",

             consumer->id());

    consumer->Discard();

    return;

  }

  if (posted_buffers_.IsFull()) {

    ALOGE("Error: posted buffers full, overwriting");

    posted_buffers_.PopBack();