Removed passwordShouldAutocomplete from WebPasswordFormData. Now that we are
ignoring autocomplete='off', this property is no longer used and is irrelevant.

Review URL: https://codereview.chromium.org/93943003

git-svn-id: svn://svn.chromium.org/blink/trunk@163224 bbb929c8-8fbe-4397-9dbb-9b2b20218538