Get the basics of deferred libraries working.

pkg/dev_compiler/lib/js/common/dart_sdk.js

Index: pkg/dev_compiler/lib/js/common/dart_sdk.js
diff --git a/pkg/dev_compiler/lib/js/common/dart_sdk.js b/pkg/dev_compiler/lib/js/common/dart_sdk.js
index 66153919fa4fdb0b64b5c8d76442156df095f113..f23ad0e4c2238253753fb744ed0014a6fbd8983f 100644
--- a/pkg/dev_compiler/lib/js/common/dart_sdk.js
+++ b/pkg/dev_compiler/lib/js/common/dart_sdk.js
@@ -1938,6 +1938,9 @@
     }
     return name;
   };
+  dart.loadLibrary = function() {
+    return async.Future.value();
+  };
   dart.defineProperty = function(obj, name, desc) {
     return Object.defineProperty(obj, name, desc);
   };