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This is an incremental fix for 438313 that addresses the two issues mentioned here:
https://code.google.com/p/chromium/issues/detail?id=438313#c24
This issues are reproducible only with the alpha server with
implicit permanent folders enabled. I added a test case for
one of them - the out of order deletion which results in
deleting the permanent folder for a datatype before some of
the items of the same datatype. That occurs only in one
particular corner case when a failed datatype need to be
purged and re-downloaded.

BUG=438313

Review URL: https://codereview.chromium.org/1139883007

Cr-Commit-Position: refs/heads/master@{#330657}