Reviewed by timo, ggaren.

    Reviewed by timo, ggaren.

        Make Icon ref-counted.

        * platform/FileChooser.h: Store m_icon as a RefPtr instead of
        auto_ptr.
        * platform/Icon.h: Inherit from Shared<Icon>
        * platform/mac/FileChooserMac.mm:
        (WebCore::FileChooser::chooseFile): Update m_icon usage
        * platform/mac/IconMac.mm:
        (WebCore::Icon::newIconForFile): Return a RefPtr instead of an
        auto_ptr

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@16336 268f45cc-cd09-0410-ab3c-d52691b4dbfc