Use static strings in autofill labeling.

Local profiling shows a significant chunk of time goes into creating strings.
Using static strings appears to resolve the performance issues seen in 173243
when tested locally.

BUG=173243


Review URL: https://chromiumcodereview.appspot.com/12220070

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@181751 0039d316-1c4b-4281-b951-d872f2087c98
1 file changed