SVGTests should not leave detached elements in the tree

LayoutTests/svg/dynamic-updates/resources/SVGTestCase.js

 // Force activating pixel tests - this variable is used in fast/js/resources/js-test-pre.js, when calling setDumpAsText().
 window.enablePixelTesting = true;
 
 var svgNS = "http://www.w3.org/2000/svg";
 var xlinkNS = "http://www.w3.org/1999/xlink";
 var xhtmlNS = "http://www.w3.org/1999/xhtml";
 
 var rootSVGElement;
 var iframeElement;
 
 function createSVGElement(name) {
     return document.createElementNS(svgNS, "svg:" + name);
 }
 
+function shouldHaveBBox(element, width, height)
+{
+    shouldBe(element + ".getBBox().width", width);
+    shouldBe(element + ".getBBox().height", height);
+}
+
 function createSVGTestCase() {
     if (window.testRunner)
         testRunner.waitUntilDone();
 
     rootSVGElement = createSVGElement("svg");
     rootSVGElement.setAttribute("width", "300");
     rootSVGElement.setAttribute("height", "300");
 
     var bodyElement = document.documentElement.lastChild;
     bodyElement.insertBefore(rootSVGElement, document.getElementById("description"));
@@ skipping 32 matching lines @@
     var script = document.createElement("script");
 
     script.onload = function() {
         if (window.testRunner)
             testRunner.notifyDone();
     };
 
     script.src = "../../fast/js/resources/js-test-post.js";
     document.body.appendChild(script);
 }