SELECT element: Fix a DCHECK failure in optionToBeShown().

If a SELECT element had a selected OPTION, but restoreFormControlState()
could't find OPTIONs matched to FormControlState, m_lastOnChangeOption had a
stale value.

Use selectOption() in restoreFormControlState() to update m_lastOnChangeOption.

BUG=627833

Review-Url: https://codereview.chromium.org/2151763002
Cr-Commit-Position: refs/heads/master@{#405447}
2 files changed