Browser plugin: Implement loadRedirect event.

content/test/data/browser_plugin_embedder.html

 <script type="text/javascript">
+var redirectOldUrl;
+var redirectNewUrl;
+function loadRedirect(event) {
+  if (event.isTopLevel) {
+    redirectOldUrl = event.oldUrl;
+    redirectNewUrl = event.newUrl;
+  }
+}
+function RedirectTo(url) {
+  var plugin = document.getElementById('plugin');
+  plugin.addEventListener('loadRedirect', loadRedirect);
+  plugin.src = url;
+}
 function SetSrc(src) {
   var plugin = document.getElementById('plugin');
   plugin.src = src;
 }
 function SetSize(w, h) {
   var plugin = document.getElementById('plugin');
   plugin.width = w;
   plugin.height = h;
 }
 function Back() {
@@ skipping 14 matching lines @@
 
 window.document.title = 'embedder';
 </script>
 
 <object id="plugin"
     tabindex="0"
     type="application/new-browser-plugin"
     width="640"
     height="480"
     border="0px"></object>