This removes the global std::set initialization.

BUG=angleproject:1389
BUG=angleproject:1459

Change-Id: I6a7f4211905ea4a83e0e2337977e2f6fb375a7dd
Reviewed-on: https://chromium-review.googlesource.com/405368Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>