Correct validation popup hiding code

When the validation popup is hidden, this unexpected code path occurs:
- HideValidationMessage() is called continuously, and keeps restarting
the timer used to call Reset()
- As a result, Reset() is never reached

The fix: do not restart the timer if a hide is in progress.

This fix is blocking an accessibility fix, which needs an accurate signal
when the validation message is no longer visible.

Bug: None
Change-Id: I0d69abf006a881dd7cc147dfe49ada50217b8c4a
Reviewed-on: https://chromium-review.googlesource.com/c/1417890
Reviewed-by: Kent Tamura <tkent@chromium.org>
Commit-Queue: Aaron Leventhal <aleventhal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#625241}
2 files changed