Restore lazy parsing of classes.

dart/lib/compiler/implementation/world.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.
 
 class World {
   Compiler compiler;  // Set in populate().
   final Map<ClassElement, Set<ClassElement>> subtypes;
 
   World() : subtypes = new Map<ClassElement, Set<ClassElement>>();
 
-  void populate(Compiler compiler, Collection<LibraryElement> libraries) {
+  void populate(Compiler compiler) {
     void addSubtypes(ClassElement cls) {
+      if (!cls.isResolved) {
+        compiler.internalErrorOnElement(
+            cls, 'Class "${cls.name.slowToString()}" is not resolved.');
+      }
       for (Type type in cls.allSupertypes) {
-        Set<Element> subtypesOfCls = subtypes.putIfAbsent(
-          type.element,
-          () => new Set<ClassElement>());
+        Set<Element> subtypesOfCls =
+          subtypes.putIfAbsent(type.element, () => new Set<ClassElement>());
         subtypesOfCls.add(cls);
       }
     }
 
-    libraries.forEach((LibraryElement library) {
-      for (Link<Element> link = library.topLevelElements;
-           !link.isEmpty();
-           link = link.tail) {
-        Element element = link.head;
-        if (!element.isClass()) continue;
-        ClassElement cls = element;
-        compiler.resolveClass(cls);
-        addSubtypes(cls);
-      }
-    });
+    compiler.resolverWorld.instantiatedClasses.forEach(addSubtypes);
 
     // Mark the world as populated.
     assert(compiler !== null);
     this.compiler = compiler;
   }
 
   /**
    * Returns a [MemberSet] that contains the possible targets of a
    * selector named [member] on a receiver whose type is [type].
    */
@@ skipping 56 matching lines @@
   final SourceString name;
 
   MemberSet(SourceString this.name) : elements = new Set<Element>();
 
   void add(Element element) {
     elements.add(element);
   }
 
   bool isEmpty() => elements.isEmpty();
 }