Get the basics of deferred libraries working.

pkg/dev_compiler/lib/js/amd/dart_sdk.js

Index: pkg/dev_compiler/lib/js/amd/dart_sdk.js
diff --git a/pkg/dev_compiler/lib/js/amd/dart_sdk.js b/pkg/dev_compiler/lib/js/amd/dart_sdk.js
index b809f1f7990ba74a9e1f1eed9d6157dd2ca5b015..de706ad07d9f5fd2ef9d98ae15a58e24e7bebcd0 100644
--- a/pkg/dev_compiler/lib/js/amd/dart_sdk.js
+++ b/pkg/dev_compiler/lib/js/amd/dart_sdk.js
@@ -1938,6 +1938,9 @@ define([], function() {
     }
     return name;
   };
+  dart.loadLibrary = function() {
+    return async.Future.value();
+  };
   dart.defineProperty = function(obj, name, desc) {
     return Object.defineProperty(obj, name, desc);
   };