Fix handling of null pointers in JS bindings.

mojo/apps/js/test/js_to_cpp_unittest.js

Index: mojo/apps/js/test/js_to_cpp_unittest.js
diff --git a/mojo/apps/js/test/js_to_cpp_unittest.js b/mojo/apps/js/test/js_to_cpp_unittest.js
index 86d395bcf5d7b1877409a72d6981db701540e12d..557b57d488417429c9b7e718f6befe397b9e2c01 100644
--- a/mojo/apps/js/test/js_to_cpp_unittest.js
+++ b/mojo/apps/js/test/js_to_cpp_unittest.js
@@ -29,11 +29,13 @@ define('mojo/apps/js/test/js_to_cpp_unittest', [
     this.cppSide_.pingResponse();
   };
 
-  JsSideConnection.prototype.echo = function (numIterations, arg) {
+  JsSideConnection.prototype.echo = function (numIterations, list) {
+    var arg = list.item;
     var arg2;
     var dataPipe1;
     var dataPipe2;
     var i;
+    var list;

[Matt Perry, 2014/05/16 18:39:04]

this looks unused

     var messagePipe1;
     var messagePipe2;
 
@@ -70,7 +72,13 @@ define('mojo/apps/js/test/js_to_cpp_unittest', [
 
       writeDataPipe(dataPipe1, senderData);
       writeDataPipe(dataPipe2, senderData);
-      this.cppSide_.echoResponse(arg, arg2);
+
+      var list = new jsToCpp.EchoArgsList();

[Matt Perry, 2014/05/16 18:39:04]

use a different variable name - this one shadows the param name

[Tom Sepez, 2014/05/16 18:57:17]

Yeah, I noticed this soon after posting this. Done.

+      list.next = new jsToCpp.EchoArgsList();
+      list.item = arg2;
+      list.next.item = arg;
+
+      this.cppSide_.echoResponse(list);
 
       core.close(dataPipe1.producerHandle);
       core.close(dataPipe2.producerHandle);