GitLab

Make it static otherwise its memory address might change between
IsAppContainerEnabled() calls and would break pointer-based identity
lookup.

R=forshaw@chromium.org

Change-Id: I775dca403a317c32ced5bd998c152849ca0413a1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2449471Reviewed-by: James Forshaw <forshaw@chromium.org>
Commit-Queue: James Forshaw <forshaw@chromium.org>
Cr-Commit-Position: refs/heads/master@{#814319}