Reviewed by Tony Chang.

        Move complexity from DataTransferItemsChromium and DataTransferItemChromium for base class
        https://bugs.webkit.org/show_bug.cgi?id=59028

        The DataTransferItemsChromium and DataTransferItemChromium code can be reused by other platforms.
        Moving the code for base class we can reduce the efforts to support DataTransferItems
        element in different platforms.

        * Android.mk:
        * CMakeLists.txt:
        * GNUmakefile.list.am:
        * WebCore.gypi:
        * WebCore.pro:
        * WebCore.vcproj/WebCore.vcproj:
        * WebCore.xcodeproj/project.pbxproj:
        * dom/DataTransferItem.cpp:
        (WebCore::DataTransferItem::DataTransferItem):
        (WebCore::DataTransferItem::owner):
        (WebCore::DataTransferItem::kind):
        (WebCore::DataTransferItem::type):
        * dom/DataTransferItem.h:
        * dom/DataTransferItems.cpp: Copied from Source/WebCore/platform/chromium/DataTransferItemsChromium.cpp.
        (WebCore::DataTransferItems::DataTransferItems):
        (WebCore::DataTransferItems::length):
        (WebCore::DataTransferItems::item):
        (WebCore::DataTransferItems::deleteItem):
        (WebCore::DataTransferItems::clear):
        (WebCore::DataTransferItems::add):
        * dom/DataTransferItems.h:
        * platform/chromium/DataTransferItemChromium.cpp:
        (WebCore::DataTransferItem::create):
        (WebCore::DataTransferItemChromium::DataTransferItemChromium):
        (WebCore::DataTransferItemChromium::getAsString):
        (WebCore::DataTransferItemChromium::getAsFile):
        * platform/chromium/DataTransferItemChromium.h:
        * platform/chromium/DataTransferItemsChromium.cpp:
        (WebCore::DataTransferItemsChromium::DataTransferItemsChromium):
        * platform/chromium/DataTransferItemsChromium.h:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@84857 268f45cc-cd09-0410-ab3c-d52691b4dbfc