Deferred (aka lazy) loading of static functions.

dart/sdk/lib/_internal/compiler/implementation/lib/js_helper.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library _js_helper;
 
 import 'dart:collection';
 import 'dart:_foreign_helper' show DART_CLOSURE_TO_JS,
                                    JS,
                                    JS_CALL_IN_ISOLATE,
@@ skipping 504 matching lines @@
   static getConstructor(String className) {
     // TODO(ahe): How to safely access $?
     return JS('var', r'$[#]', className);
   }
 
   static bool identicalImplementation(a, b) {
     return JS('bool', '# == null', a)
       ? JS('bool', '# == null', b)
       : JS('bool', '# === #', a, b);
   }
+
+  // Used to implement deferred loading. Used as callback on "load"

[ahe, 2013/02/04 17:46:29]

I should be able to move these methods into async_patch now that _foreign_helper
is imported explicitly.

[ahe, 2013/02/05 13:54:22]

Done.

+  // event by async_patch.dart.
+  static onDeferredLibraryLoadClosure(/* Completer<bool> */ completer, event) {
+    completer.complete(true);
+  }
+
+  static onDeferredLibraryLoad() {
+    return DART_CLOSURE_TO_JS(onDeferredLibraryLoadClosure);
+  }
 }
 
 /**
  * Called by generated code to throw an illegal-argument exception,
  * for example, if a non-integer index is given to an optimized
  * indexed access.
  */
 iae(argument) {
   throw new ArgumentError(argument);
 }
@@ skipping 960 matching lines @@
   if (len != t.length) return false;
   for (int i = 1; i < len; i++) {
     if (!isSubtype(s[i], t[i])) {
       return false;
     }
   }
   return true;
 }
 
 createRuntimeType(String name) => new TypeImpl(name);