This patch moves all the code related to Toggle from Instance.cpp to
Toggles.cpp to make the code in Instance.cpp cleaner.
BUG=dawn:56
Change-Id: Ica2a779569478a58ddf21e632a211c0c5b889b00
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/9580
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Austin Eng <enga@chromium.org>
Commit-Queue: Jiawei Shao <jiawei.shao@intel.com>
