Fix typo in StyleResolverState.h

Introduced in https://src.chromium.org/viewvc/blink?view=rev&revision=154076

Causes a crash when using DevTools in Android WebView, see b/9854659

R=dglazkov@chromium.org

Review URL: https://codereview.chromium.org/19192004

git-svn-id: svn://svn.chromium.org/blink/trunk@154295 bbb929c8-8fbe-4397-9dbb-9b2b20218538