GitLab

AppendExtraBrowserArgs takes only one flag at a time. Fix
v8.browsing_desktop-future and v8.browsing_mobile-future to
call AppendExtraBrowserArgs twice to pass two flags.

Bug: 
Change-Id: I85bfe7b69be2164a26d77a9bc8bacb7272eff10f
Reviewed-on: https://chromium-review.googlesource.com/814437Reviewed-by: Ned Nguyen <nednguyen@google.com>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Commit-Queue: Mythri Alle <mythria@chromium.org>
Cr-Commit-Position: refs/heads/master@{#522472}