Reviewed by Adam Barth.

        Move m_context out of generator into a superclass
        https://bugs.webkit.org/show_bug.cgi?id=27521

        Mostly this is removing code from CodeGeneratorJS
        and instead using a DOMObjectWithSVGContext superclass in JSDOMBinding.h.

        DOMObjectWithSVGContext.h is its own file so that WebKit doesn't need to
        know about SVGElement.h (WebKit includes JSDOMBinding.h for some reason).

        I also removed context pointer from SVGZoomEvent since it was never used.

        * WebCore.gypi:
        * WebCore.pro:
        * WebCore.vcproj/WebCore.vcproj:
        * WebCore.xcodeproj/project.pbxproj:
        * bindings/js/DOMObjectWithSVGContext.h: Added.
        (WebCore::DOMObjectWithSVGContext::context):
        (WebCore::DOMObjectWithSVGContext::DOMObjectWithSVGContext):
        * bindings/js/JSDOMBinding.h:
        * bindings/js/JSEventCustom.cpp:
        (WebCore::toJS):
        * bindings/scripts/CodeGeneratorJS.pm:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@46201 268f45cc-cd09-0410-ab3c-d52691b4dbfc