Don't reset the database when there was an I/O error.

Unlike corruption errors, I/O errors have the potential to be ephemeral.
We shouldn't aggressively delete the database in those cases. Instead,
punt that decision up to the web app.

Also, can remove the full disk catch-all. That was intended to catch
full disks masquerading as other I/O errors.

BUG=239882

Review URL: https://codereview.chromium.org/26045002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@227444 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 227444