Added full deferred loading semantic to precompiled/--noopt/eager-loading code

runtime/lib/lib_prefix.dart

 // Copyright (c) 2014, 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.
 
 import "dart:async";
 import "dart:isolate";
 
 // This type corresponds to the VM-internal class LibraryPrefix.
 class _LibraryPrefix {
 
   bool _load() native "LibraryPrefix_load";
   Error _loadError() native "LibraryPrefix_loadError";
+  bool isLoaded() native "LibraryPrefix_isLoaded";
 
   bool _invalidateDependentCode()
       native "LibraryPrefix_invalidateDependentCode";
 
   loadLibrary() {
     var completer = _outstandingLoadRequests[this];
     if (completer != null) {
       return completer.future;
     }
     completer = new Completer<bool>();
@@ skipping 25 matching lines @@
     var error = prefix._loadError();
     if (error != null) {
       completer.completeError(error);
     } else {
       prefix._invalidateDependentCode();
       completer.complete(true);
     }
   });
   _outstandingLoadRequests.clear();
 }