Ensure supertypes are loaded safely.

dart/lib/compiler/implementation/ssa/builder.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 Interceptors {
   Compiler compiler;
   Interceptors(Compiler this.compiler);
 
   SourceString mapOperatorToMethodName(Operator op) {
     String name = op.source.stringValue;
@@ skipping 970 matching lines @@
       }
     }
 
     if (!foundSuperOrRedirect) {
       // No super initializer found. Try to find the default constructor if
       // the class is not Object.
       ClassElement enclosingClass = constructor.getEnclosingClass();
       ClassElement superClass = enclosingClass.superclass;
       if (enclosingClass != compiler.objectClass) {
         assert(superClass !== null);
-        assert(superClass.isResolved);
+        assert(superClass.resolutionState == ClassElement.STATE_DONE);
         FunctionElement target = superClass.lookupConstructor(superClass.name);
         if (target === null) {
           compiler.internalError("no default constructor available");
         }
         inlineSuperOrRedirect(target,
                               Selector.INVOCATION_0,
                               const EmptyLink<Node>(),
                               constructors,
                               fieldValues);
       }
@@ skipping 2612 matching lines @@
           new HSubGraphBlockInformation(elseBranch.graph));
 
     HBasicBlock conditionStartBlock = conditionBranch.block;
     conditionStartBlock.setBlockFlow(info, joinBlock);
     SubGraph conditionGraph = conditionBranch.graph;
     HIf branch = conditionGraph.end.last;
     assert(branch is HIf);
     branch.blockInformation = conditionStartBlock.blockFlow;
   }
 }