Browser plugin: Implement titleChanged event.

content/test/data/browser_plugin_embedder.html

Index: content/test/data/browser_plugin_embedder.html
diff --git a/content/test/data/browser_plugin_embedder.html b/content/test/data/browser_plugin_embedder.html
index 45b374e3ac9f9d91494114f5cfb0b6418c9a0168..1b85e378b1eb405caf3f23b7f9f59145daaf2540 100644
--- a/content/test/data/browser_plugin_embedder.html
+++ b/content/test/data/browser_plugin_embedder.html
@@ -14,6 +14,11 @@ function loadRedirect(event) {
     redirectNewUrl = event.newUrl;
   }
 }
+var shouldEchoTitle = false;
+function titleChanged(evt) {
+  if (shouldEchoTitle)
+    document.title = evt.title;
+}
 function SetSrc(src) {
   var plugin = document.getElementById('plugin');
   plugin.src = src;
@@ -53,4 +58,5 @@ document.title = 'embedder';
   plugin.addEventListener('loadStart', loadStart);
   plugin.addEventListener('loadAbort', loadAbort);
   plugin.addEventListener('loadRedirect', loadRedirect);
+  plugin.addEventListener('titleChanged', titleChanged);
 </script>