Update WebDialog to handle cases with not yet created session

Bug: 937027
Change-Id: Ifc432c2c1401c54ebcd3cfa9b7b52971e4b50b47
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1520683
Commit-Queue: Anatoliy Potapchuk <apotapchuk@chromium.org>
Reviewed-by: Bret Sepulveda <bsep@chromium.org>
Cr-Commit-Position: refs/heads/master@{#640703}
1 file changed