Fix build breakage.

lib/compiler/implementation/ssa/optimize.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.
 
 abstract class OptimizationPhase {
   String get name;
   void visitGraph(HGraph graph);
 }
 
 class SsaOptimizerTask extends CompilerTask {
@@ skipping 230 matching lines @@
       if (transformToDynamicInvocation) {
         return fromInterceptorToDynamicInvocation(node, node.selector);
       }
     }
 
     return node;
   }
 
   bool isFixedSizeListConstructor(HInvokeStatic node) {
     Element element = node.inputs[0].element;
+    DartType defaultClass = compiler.listClass.defaultClass;
+    // TODO(ngeoffray): make sure that the only reason the List class is
+    // not resolved is because it's not being used.
     return element.isConstructor()
-        && element.enclosingElement == compiler.listClass.defaultClass.element
+        && defaultClass != null
+        && element.enclosingElement.declaration == defaultClass.element
         && node.inputs.length == 2
         && node.inputs[1].isInteger(types);
   }
 
   HInstruction visitInvokeStatic(HInvokeStatic node) {
     if (isFixedSizeListConstructor(node)) {
       node.guaranteedType = HType.FIXED_ARRAY;
     }
     return node;
   }
@@ skipping 1070 matching lines @@
     }
 
     // For other fields having setters in the generative constructor body, set
     // the type to UNKNOWN to avoid relying on the type set in the initializer
     // list.
     allSetters.forEach((Element element) {
       backend.registerFieldConstructor(element, HType.UNKNOWN);
     });
   }
 }