Allow to toggle multiple features with parameters in js tests.

Bug: 
Change-Id: Ib95e3d97f5d6331e8caa9c0d2209785a2ac52141
Reviewed-on: https://chromium-review.googlesource.com/c/1454580
Commit-Queue: Alexander Yashkin <a-v-y@yandex-team.ru>
Reviewed-by: Tommy Li <tommycli@chromium.org>
Reviewed-by: David Tseng <dtseng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#632135}
3 files changed