REGRESSION: Menulist SELECT doesn't update display value on OSX and Android.

This bug was exposed by [1], which corrected RenderMenuList::m_popupIsVisible
flag on OSX and Android.

ExternalPopupMenu::didAcceptIndex called PopupMenuClient::valueChanged then
PopupMenuClient::popupDidHide. This made the bug with the follwoing steps:

1. Calls PopupMenuClient::valueChanged.
2. It dispatches a 'change' event
3. The event handler does 'select.selectedIndex = newValue'.
4. Because the PopupMenuClient assumes the popup is still visible, it doesn't
  update the display value.
5. Return to ExternalPopupMenu::didAcceptIndex, and calls
  PopupMenuClient::popupDidHide
(If the event handle didn't update the selectedIndex,
RenderMenuList::updateFromElement would be called and the display value would be
updated correctly.)

This CL change the order of valueChanged and popupDidHide.  This matches to
PopupListBox, the popup implementation for Windows, Linux, and ChromiumOS.

[1] http://src.chromium.org/viewvc/blink?view=rev&revision=169901

BUG=363064
TEST=See crbug.com/363064. We can't make an automated test for popup behavior.

Review URL: https://codereview.chromium.org/237533010

git-svn-id: svn://svn.chromium.org/blink/trunk@171763 bbb929c8-8fbe-4397-9dbb-9b2b20218538