libaddressinput - minor optimization: don't copy a couple of small strings

BUG=337679

Review URL: https://codereview.chromium.org/146243003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@248061 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 248061