drive: Add util::GetIdentityResourceIdCanonicalizer()

To share the same implementation.

BUG=None
TEST=build
R=kinaba@chromium.org

Review URL: https://codereview.chromium.org/28673002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@229743 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 229743