Implement a part of ProcessingInstruction by using PrivateScript

LayoutTests/fast/xsl/resources/test-xslt.js

+if (window.testRunner)
+    testRunner.waitUntilDone();
+
+var _NUM_RETRIES = 10;
+var _TIMEOUT = 200;
+
+function waitXSLTransform(iframe, callback) {
+    var oldDocument = iframe.contentDocument;
+    var retry = _NUM_RETRIES;
+
+    function waitXSLTransformInternal() {
+        if (--retry && oldDocument == iframe.contentDocument)
+            setTimeout(waitXSLTransformInternal, _TIMEOUT);
+
+        callback();
+        if (window.testRunner)
+            testRunner.notifyDone();
+    };
+    setTimeout(waitXSLTransformInternal, _TIMEOUT);
+}
+
+function runTest(url) {
+    var iframe = document.createElement('iframe');
+    iframe.src = url;
+    document.body.appendChild(iframe);
+    waitXSLTransform(iframe, function() {});
+};