Add encounteredError() to AssociatedInterfacePtrController.

mojo/public/js/lib/interface_endpoint_client.js

Index: mojo/public/js/lib/interface_endpoint_client.js
diff --git a/mojo/public/js/lib/interface_endpoint_client.js b/mojo/public/js/lib/interface_endpoint_client.js
index b74b6d203acb5078adab193597d2932a667f092c..3235434d666ac270558eaadc0bfe3b2134e64329 100644
--- a/mojo/public/js/lib/interface_endpoint_client.js
+++ b/mojo/public/js/lib/interface_endpoint_client.js
@@ -232,6 +232,10 @@ define("mojo/public/js/lib/interface_endpoint_client", [
     this.controlMessageProxy_.requireVersion(version);
   };
 
+  InterfaceEndpointClient.prototype.getEncounteredError = function() {
+    return this.encounteredError_;
+  };
+
   var exports = {};
   exports.InterfaceEndpointClient = InterfaceEndpointClient;