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Based on logging (see earlier patchsets), it appears the existing data
base can cause the test update to be thrown out resulting in test
failures. It seems flakey whether the data base is persisted, so
purging it will likely fix many flakes.

Secondly, I am turning the tests off on chromeOS there are some dependencies
on file reads that seem to be flaky on ChromeOS, so it's easier to turn them
off.

Change-Id: I9535e7c6d855bdb7573a0c0e03868699dabcdf88
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1497368Reviewed-by: Tarun Bansal <tbansal@chromium.org>
Commit-Queue: Ryan Sturm <ryansturm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#637896}