Add functions for autocomplete, selectionRange, directioinForFormData for TextArea element.

R=isherman@chromium.org, tkent@chromium.org
BUG=332557

Review URL: https://codereview.chromium.org/167383002

git-svn-id: svn://svn.chromium.org/blink/trunk@167347 bbb929c8-8fbe-4397-9dbb-9b2b20218538