Reviewed by Oliver Hunt.

        Instead of relying on Object.prototype.toString result use JSObject::isActivationObject
        to check if a scope node is a JSActivation. Object.prototype.toString for JSActivation
        will call JSActivation::toThisObject whose result depends on the current call stack.

        https://bugs.webkit.org/show_bug.cgi?id=34161

        Test: WebCore/manual-tests/inspector/debugger-scopes-inspection.html

        * bindings/js/JSInjectedScriptHostCustom.cpp:
        (WebCore::JSInjectedScriptHost::isActivation):
        * inspector/InjectedScriptHost.idl:
        * inspector/front-end/InjectedScript.js:
        (injectedScriptConstructor.):
        * manual-tests/inspector/debugger-scopes-inspection.html: Added.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@53945 268f45cc-cd09-0410-ab3c-d52691b4dbfc