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This fixes the crash observed in crbug.com/1166233 and adds tests for
it. See the comments in that bug for more details.

This fix also removes the dialog for unauthorized users for pasting
after the initial scan that does authentication, so crbug.com/1028133
is affected.

Bug: 1166233, 1028133
Change-Id: Id3c992fdeccfa92a9f88e25c13e7a15bcb1afd8c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2633701Reviewed-by: anthonyvd <anthonyvd@chromium.org>
Commit-Queue: Dominique Fauteux-Chapleau <domfc@chromium.org>
Cr-Commit-Position: refs/heads/master@{#844787}