Make DOMImplementation.hasFeature() always return true.

LayoutTests/svg/dynamic-updates/script-tests/SVGGElement-svgdom-requiredFeatures.js

-// [Name] SVGGElement-svgdom-requiredFeatures.js
-// [Expected rendering result] a series of PASS messages
-
-createSVGTestCase();
-
-var gElement = createSVGElement("g");
-var imageElement = createSVGElement("image");
-imageElement.setAttribute("width", "200");
-imageElement.setAttribute("height", "200");
-
-gElement.appendChild(imageElement);
-rootSVGElement.appendChild(gElement);
-
-function repaintTest() {
-    debug("Check that SVGGElement is initially displayed");
-    shouldHaveBBox("gElement.firstElementChild", "200", "200");
-    debug("Check that setting requiredFeatures to something invalid makes it not render");
-    gElement.requiredFeatures.appendItem("http://www.w3.org/TR/SVG11/feature#BogusFeature");
-    shouldHaveBBox("gElement.firstElementChild", "0", "0");
-    debug("Check that setting requiredFeatures to something valid makes it render again");
-    gElement.requiredFeatures.replaceItem("http://www.w3.org/TR/SVG11/feature#Shape", 0);
-    shouldHaveBBox("gElement.firstElementChild", "200", "200");
-    debug("Check that adding something valid to requiredFeatures keeps rendering the element");
-    gElement.requiredFeatures.appendItem("http://www.w3.org/TR/SVG11/feature#Gradient");
-    shouldHaveBBox("gElement.firstElementChild", "200", "200");
-    debug("Check that adding something invalid to requiredFeatures makes it not render");
-    gElement.requiredFeatures.appendItem("http://www.w3.org/TR/SVG11/feature#BogusFeature");
-    shouldHaveBBox("gElement.firstElementChild", "0", "0");
-}
-
-var successfullyParsed = true;