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This histogram will also tell us how often the server response got back
too late and the timeout was reached.

This CL also makes sure we always send back the file hash if the
enhanced download protection is enabled.

BUG=NONE
TEST=Run all unit-tests under DownloadProtectionServiceTest.

Review URL: http://codereview.chromium.org/8600006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@110801 0039d316-1c4b-4281-b951-d872f2087c98