Support for a dart2js `dartDeferredLoader` hook.

sdk/lib/_internal/compiler/js_lib/preambles/d8.js

Index: sdk/lib/_internal/compiler/js_lib/preambles/d8.js
diff --git a/sdk/lib/_internal/compiler/js_lib/preambles/d8.js b/sdk/lib/_internal/compiler/js_lib/preambles/d8.js
index aed01611236ecf870687224cf08f78c8f0dc32fb..ee58aa6b49312385408ce50380d26406ba306fa2 100644
--- a/sdk/lib/_internal/compiler/js_lib/preambles/d8.js
+++ b/sdk/lib/_internal/compiler/js_lib/preambles/d8.js
@@ -280,4 +280,13 @@ if (typeof global != "undefined") self = global;  // Node.js.
   self.clearInterval = cancelTimer;
   self.scheduleImmediate = addTask;
   self.self = self;

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

Create a "section" (with a comment).

Keep 'self.self = self' last (or move it to the very top).

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

Done.

+  self.dartDeferredLibraryLoader =
+    function(uri, successCallback, errorCallback) {
+      try {
+        (new Function(load(uri)))();

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

What is the "new Function" supposed to do?
I think "load" will load *and* execute the script in the top-level scope, and
then return undefined.
You are basically loading it, and then doing "new Function(undefined)()".

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

Yes, I realized that this morning also.

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