Remove SandboxMountPointProvier::GetBaseDirectoryForOrigin as it's no longer used

A tiny cleanup.

BUG=none
TEST=green bots

Review URL: http://codereview.chromium.org/7372001

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@92654 0039d316-1c4b-4281-b951-d872f2087c98
5 files changed