message: Add TODO regarding handling of existing fp16 nodes
diff: @@ -1392,6 +1392,9 @@ void AutoMixedPrecisionImpl::AddClearAndGrayToWhiteIfBetweenWhite(
  (!downstream_of_white_set.count(idx) &&
  !fp16_whitelist_.count(item.node->op()) &&
  !black_set.count(idx) && ShouldProcess(*item.node) &&
  + // TODO(benbarsdell): Consider allowing propagation through
  + // ops that are already float16 in order to reduce the number
  + // of casts.
  IsFloat32(item) && SupportsFloat16(item) &&
  (fp16_clearlist_.count(item.node->op()) ||
  fp16_graylist_.count(item.node->op())));
  