Support for a dart2js `dartDeferredLoader` hook.

sdk/lib/_internal/compiler/js_lib/preambles/jsshell.js

Index: sdk/lib/_internal/compiler/js_lib/preambles/jsshell.js
diff --git a/sdk/lib/_internal/compiler/js_lib/preambles/jsshell.js b/sdk/lib/_internal/compiler/js_lib/preambles/jsshell.js
index 8f13bcc8f28fefa1adcad3488d1746cf590c35c1..51c29ad9f0ff1873a70a2aaa1779e4e1f999a540 100644
--- a/sdk/lib/_internal/compiler/js_lib/preambles/jsshell.js
+++ b/sdk/lib/_internal/compiler/js_lib/preambles/jsshell.js
@@ -16,4 +16,15 @@
   // Global properties. "self" refers to the global object, so adding a
   // property to "self" defines a global variable.
   self.self = self;
+
+  self.dartDeferredLibraryLoader =
+  function(uri, successCallback, errorCallback) {
+    print("Loading "+uri);

[floitsch, 2015/02/25 16:00:00]

Remove?

[sigurdm, 2015/02/26 13:19:05]

Done.

+    try {
+      (new Function(load(uri)))();

[Lasse Reichstein Nielsen, 2015/02/26 08:44:09]

Remove Function here too.

[sigurdm, 2015/02/26 13:19:05]

Done.

+      successCallback();
+    } catch (error) {
+      errorCallback(error);
+    }
+  };
 })(this)