Added predictor class for AssistRanker NN classifier.

Added a predictor class for the new NN classifier in AssistRanker. This
makes it possible to use downloadable unquantized NN classifiers for
inferencing.

Bug: 907727
Change-Id: Ib1e5647e3792f10757c17968a6b0b9b198a8d620
Reviewed-on: https://chromium-review.googlesource.com/c/1399768
Commit-Queue: Jon Napper <napper@chromium.org>
Reviewed-by: Charles . <charleszhao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#625104}
9 files changed