Make DOMImplementation.hasFeature() always return true.

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

-// [Name] SVGLineElement-svgdom-requiredFeatures.js
-// [Expected rendering result] a series of PASS messages
-
-createSVGTestCase();
-
-var lineElement = createSVGElement("line");
-lineElement.setAttribute("x1", "20");
-lineElement.setAttribute("y1", "20");
-lineElement.setAttribute("x2", "200");
-lineElement.setAttribute("y2", "200");
-lineElement.setAttribute("stroke", "green");
-lineElement.setAttribute("stroke-width", "10px");
-
-rootSVGElement.appendChild(lineElement);
-
-function repaintTest() {
-    description("Check that SVGLineElement is initially displayed");
-    shouldHaveBBox("lineElement", "180", "180");
-    description("Check that setting requiredFeatures to something invalid makes it not render");
-    lineElement.requiredFeatures.appendItem("http://www.w3.org/TR/SVG11/feature#BogusFeature");
-    shouldHaveBBox("lineElement", "0", "0");
-    description("Check that setting requiredFeatures to something valid makes it render again");
-    lineElement.requiredFeatures.replaceItem("http://www.w3.org/TR/SVG11/feature#Shape", 0);
-    shouldHaveBBox("lineElement", "180", "180");
-    debug("Check that adding something valid to requiredFeatures keeps rendering the element");
-    lineElement.requiredFeatures.appendItem("http://www.w3.org/TR/SVG11/feature#Gradient");
-    shouldHaveBBox("lineElement", "180", "180");
-    debug("Check that adding something invalid to requiredFeatures makes it not render");
-    lineElement.requiredFeatures.appendItem("http://www.w3.org/TR/SVG11/feature#BogusFeature");
-    shouldHaveBBox("lineElement", "0", "0");
-}
-
-var successfullyParsed = true;