Make JavaScript binding for Clipboard::types more normal
https://bugs.webkit.org/show_bug.cgi?id=120271

Reviewed by Anders Carlsson.

* bindings/js/JSClipboardCustom.cpp:
(WebCore::JSClipboard::types): Make a simple custom binding. Only needed because
there is a special value, null, this can return.

* dom/Clipboard.cpp:
(WebCore::Clipboard::types): Return Vector<String> instead of ListHashSet<String>.
* dom/Clipboard.h: Ditto.
* platform/Pasteboard.h: Ditto.
* platform/blackberry/PasteboardBlackBerry.cpp:
(WebCore::Pasteboard::types): Ditto.
* platform/efl/PasteboardEfl.cpp:
(WebCore::Pasteboard::types): Ditto.
* platform/gtk/PasteboardGtk.cpp:
(WebCore::Pasteboard::types): Ditto.
* platform/ios/PasteboardIOS.mm:
(WebCore::Pasteboard::types): Ditto.
* platform/mac/PasteboardMac.mm:
(WebCore::Pasteboard::types): Ditto.
* platform/qt/PasteboardQt.cpp:
(WebCore::Pasteboard::types): Ditto.
* platform/win/PasteboardWin.cpp:
(WebCore::Pasteboard::types): Ditto.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@154578 268f45cc-cd09-0410-ab3c-d52691b4dbfc