Should always accept menu selection by type-ahead.

Scenario:
1. Open <select> popup menu
2. Type a key to select one of options.
 -> The text in <select> box (not popup menu) is changed to the selected
    option label.
3. If a user types 'Enter' or 'Esc', the selected option is confirmed.
  However if a user clicks outside of the popup menu and remove
  focus from the <select>, selected value is reset to the initial
  value.

Both of IE and Firefox accept the selected value in the latter case.

We should always call PopupListBox::abandon() to close the popup menu.
 - PopupContainer::hidePopup is called when WebView closes a popup.
 - We make hidePopup private, but PopupContainer is still a friend of
    PopupListBox.
 - This change affects Windows, Linux, and ChromeOS. We don't use this
    code on OSX and Android.

BUG=92758
TEST=Manual. See crbug.com/92758.

Review URL: https://chromiumcodereview.appspot.com/24172006

git-svn-id: svn://svn.chromium.org/blink/trunk@158064 bbb929c8-8fbe-4397-9dbb-9b2b20218538