added hooks for add-on to replace the channel

browserid/static/dialog/resources/channel.js

@@ -17,7 +17,19 @@ function errorOut(trans, code) {
   window.self.close();
 }
 
+
 var setupChannel = function(controller) {
+  if (navigator.id && navigator.id.channel)
+    setupNativeChannel(controller);
+  else
+    setupHTMLChannel(controller);
+}
+
+var setupNativeChannel = function(controller) {
+  navigator.id.channel.registerController(controller);
+}
+
+var setupHTMLChannel = function(controller) {
   var chan = Channel.build(
     {
       window: window.opener,