Removing unused variables for parent in FocusCandidate

The variables for parent ie parentDistance and parentAlignment in
FocusCandidate are not used anymore. So removing these unused variables.

These changes has been taken from following WebKit patch:
http://trac.webkit.org/changeset/152465

Review URL: https://codereview.chromium.org/371443002

git-svn-id: svn://svn.chromium.org/blink/trunk@177602 bbb929c8-8fbe-4397-9dbb-9b2b20218538