[Quota][Pepper] Fix leak in QuotaReservationTest

BUG=194304

Review URL: https://codereview.chromium.org/100813004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@240135 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 240135