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Make sure that at most one profile corruption error dialog is shown at
any given time. Currently I ocasionally get six dialogs with an
identical error message when I start Chrome while the profile is locked.
Although, the ShowProfileErrorDialog method is called with two different
messages (corrupt profile vs incompatible profile), I have only seen one
of them showing up at any time, so the boolean guard is applied to any
dialog generated by ShowProfileErrorDialog.

R=pkasting@chromium.org
BUG=446732,447791
TEST=Manually:
1. Start Chrome to initialize the profile directory.
2. Close Chrome.
3. Mark database as read-only: chmod a-r "/tmp/profile/Default/Web Data"
4. Start Chrome again.
5. Verify that only one dialog is shown (instead of six).
6. Close Chrome.
7. Start Chrome, with the --noerrdialogs flag.
8. Verify that no error dialogs are displayed at all (instead of six).

Review URL: https://codereview.chromium.org/873253002

Cr-Commit-Position: refs/heads/master@{#314318}