[M63 Merge][Locked Fullscreen] Fix URL click tablet mode bug followup

Follow-up to crrev.com/c/1439080 - use GetRootWindow() if we're using window
service.

TBR=pkotwicz@chromium.org

(cherry picked from commit 6115145ea3747781cfda2463e988dc078d8f70d5)

Bug: 888684
Change-Id: Ifb531e9e12984048eb124c487f52ce8753cda08d
Reviewed-on: https://chromium-review.googlesource.com/c/1445894
Reviewed-by: Ivan Šandrk <isandrk@chromium.org>
Reviewed-by: Evan Stade <estade@chromium.org>
Commit-Queue: Ivan Šandrk <isandrk@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#627479}
Reviewed-on: https://chromium-review.googlesource.com/c/1447712
Cr-Commit-Position: refs/branch-heads/3683@{#88}
Cr-Branched-From: e51029943e0a38dd794b73caaf6373d5496ae783-refs/heads/master@{#625896}
1 file changed