GitLab

ShowWarningBanner() and HideWarningBanner() are combined into
UpdateWarningMessage().

TBR=tsepez@chromium.org

Bug: 958206
Change-Id: I1569d2cec960357c5e6151bdfc32800be495c268
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1629428
Commit-Queue: Evan Stade <estade@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#663978}