Make DOMImplementation.hasFeature() always return true.

LayoutTests/svg/dynamic-updates/script-tests/SVGSVGElement-dom-requiredFeatures.js

-// [Name] SVGSVGElement-dom-requiredFeatures.js
-// [Expected rendering result] a series of PASS messages
-
-createSVGTestCase();
-
-var svgElement = rootSVGElement;
-
-function repaintTest() {
-    debug("Check that SVGSVGElement is initially displayed");
-    shouldBe("svgElement.getBoundingClientRect().width", "300");
-    debug("Check that setting requiredFeatures to something invalid makes it not render");
-    svgElement.setAttribute("requiredFeatures", "http://www.w3.org/TR/SVG11/feature#BogusFeature");
-    shouldBe("svgElement.getBoundingClientRect().width", "0");
-    debug("Check that setting requiredFeatures to something valid makes it render again");
-    svgElement.setAttribute("requiredFeatures", "http://www.w3.org/TR/SVG11/feature#Shape");
-    shouldBe("svgElement.getBoundingClientRect().width", "300");
-    debug("Check that adding something valid to requiredFeatures keeps rendering the element");
-    svgElement.setAttribute("requiredFeatures", "http://www.w3.org/TR/SVG11/feature#Gradient");
-    shouldBe("svgElement.getBoundingClientRect().width", "300");
-    debug("Check that adding something invalid to requiredFeatures makes it not render");
-    svgElement.setAttribute("requiredFeatures", "http://www.w3.org/TR/SVG11/feature#BogusFeature");
-    shouldBe("svgElement.getBoundingClientRect().width", "0");
-}
-
-
-var successfullyParsed = true;