HTMLOptionElement code style: consistently access select owner.

For methods that access the select owner, do this consistently
when otherwise possible.

R=
BUG=

Review URL: https://codereview.chromium.org/109533003

git-svn-id: svn://svn.chromium.org/blink/trunk@164189 bbb929c8-8fbe-4397-9dbb-9b2b20218538