Fix an issue found in https://chromiumcodereview.appspot.com/23205008/
Min granularity was still not being calculated right. Fix it again and add a unit test.

BUG=268300

Review URL: https://codereview.chromium.org/141883002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@245611 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 245611
Stub for Privet file system

This contains a stub Privet file system, behind a flag.

BUG=332182

Review URL: https://codereview.chromium.org/120533006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@245612 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 245612