Create type masks lazily.

sdk/lib/_internal/compiler/implementation/elements/elements.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 elements;
 
 
 import '../tree/tree.dart';
 import '../util/util.dart';
 import '../resolution/resolution.dart';
@@ skipping 805 matching lines @@
   bool get hasConstructor;
   Link<Element> get constructors;
 
   ClassElement get patch;
   ClassElement get origin;
   ClassElement get declaration;
   ClassElement get implementation;
 
   int get supertypeLoadState;
   int get resolutionState;
+  bool get isResolved;
   SourceString get nativeTagInfo;
 
   bool get isMixinApplication;
   bool get isUnnamedMixinApplication;
   bool get hasBackendMembers;
   bool get hasLocalScopeMembers;
 
   // TODO(kasperl): These are bit fishy. Do we really need them?
   void set thisType(InterfaceType value);
   void set supertype(DartType value);
@@ skipping 108 matching lines @@
   int get resolutionState;
   Token get beginToken;
   Token get endToken;
 
   // TODO(kasperl): Try to get rid of these.
   void set annotatedElement(Element value);
   void set resolutionState(int value);
 
   MetadataAnnotation ensureResolved(Compiler compiler);
 }