browser-plugin: Send a JSON string for the detail data with the events.

content/test/data/browser_plugin_embedder.html

 <script type="text/javascript">
 function loadAbort(evt) {
-  document.title = evt.detail.reason;
+  document.title = JSON.parse(evt.detail).reason;
 }
 function loadStart(evt) {
-  document.title = evt.detail.url;
+  document.title = JSON.parse(evt.detail).url;
 }
 function loadStop(evt) {
   document.title = "loadStop";
 }
 
 var commitIsTopLevel;
 function loadCommit(evt) {
-  document.title = "loadCommit:" + evt.detail.url;
-  commitIsTopLevel = evt.detail.isTopLevel;
+  var detail = JSON.parse(evt.detail);
+  document.title = "loadCommit:" + detail.url;
+  commitIsTopLevel = detail.isTopLevel;
 }
 
 var redirectOldUrl;
 var redirectNewUrl;
 function loadRedirect(event) {
   document.title = "redirected";
-  if (event.detail.isTopLevel) {
-    redirectOldUrl = event.detail.oldUrl;
-    redirectNewUrl = event.detail.newUrl;
+  var detail = JSON.parse(event.detail);
+  if (detail.isTopLevel) {
+    redirectOldUrl = detail.oldUrl;
+    redirectNewUrl = detail.newUrl;
   }
 }
 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;
@@ skipping 60 matching lines @@
   }
 }
   var plugin = document.getElementById('plugin');
   plugin.addEventListener('-internal-loadstart', loadStart);
   plugin.addEventListener('-internal-loadabort', loadAbort);
   plugin.addEventListener('-internal-loadredirect', loadRedirect);
   window.addEventListener('message', receiveMessage, false);
   plugin.addEventListener('-internal-loadstop', loadStop);
   plugin.addEventListener('-internal-loadcommit', loadCommit);
 </script>