Simplify protocol between SELECT elements and popups.

- Rename listBoxSelectItem to selectMultipleOptionsByPopup, and it accepts index
  vector.
- Rename valueChanged to selectOptionByPopup.

Single-selection menulist accepts only selectOptionByPopup().
Multiple-selection menulist accepts selectOptionByPopup(-1) and
selectMultipleOptionsByPopup().

Review-Url: https://codereview.chromium.org/2143863003
Cr-Commit-Position: refs/heads/master@{#405134}
4 files changed