bindings: Fixes layouttests when moving attributes to prototype chains.

LayoutTests/resources/js-test.js

 // js-test now supports lazily printing test results which dumps all test
 // results once at the end of the test instead of building them up. To enable
 // this option, call setPrintTestResultsLazily() before running any tests.
 var _lazyTestResults; // Set by setPrintTestResultsLazily().
 
 // svg/dynamic-updates tests set enablePixelTesting=true, as we want to dump text + pixel results
 if (self.testRunner) {
     if (self.enablePixelTesting)
         testRunner.dumpAsTextWithPixelResults();
     else
@@ skipping 181 matching lines @@
 
 function stringify(v)
 {
     if (isNewSVGTearOffType(v))
         return v.valueAsString;
     if (v === 0 && 1/v < 0)
         return "-0";
     else return "" + v;
 }
 
+// Stringifies a DOM object.  This function stringifies not only own properties
+// but also DOM attributes which are on a prototype chain.  Note that
+// JSON.stringify only stringifies own properties.
+function stringifyDOMObject(object)
+{
+    function deepCopy(src) {
+        if (typeof src != "object")
+            return src;
+        var dst = src instanceof Array ? [] : {};

[jsbell, 2015/01/21 18:09:39]

Nit: Use Array.isArray()

(instanceof doesn't work across 'realms')

[Yuki, 2015/01/22 06:53:29]

Done.

+        for (var property in src) {
+            dst[property] = deepCopy(src[property]);
+        }
+        return dst;
+    }
+    return JSON.stringify(deepCopy(object));
+}
+
 function evalAndLog(_a, _quiet)
 {
   if (typeof _a != "string")
     debug("WARN: tryAndLog() expects a string argument");
 
   // Log first in case things go horribly wrong or this causes a sync event.
   if (!_quiet)
     debug(_a);
 
   var _av;
@@ skipping 632 matching lines @@
     testPassed = function(msg) {
         workerPort.postMessage('PASS:' + msg);
     };
     finishJSTest = function() {
         workerPort.postMessage('DONE:');
     };
     debug = function(msg) {
         workerPort.postMessage(msg);
     };
 }