Access ConstantSystem through ClosedWorld.

pkg/compiler/lib/src/ssa/type_builder.dart

Index: pkg/compiler/lib/src/ssa/type_builder.dart
diff --git a/pkg/compiler/lib/src/ssa/type_builder.dart b/pkg/compiler/lib/src/ssa/type_builder.dart
index 517c091bf278ff3b63980f0e3e167ba33d5e63e8..48a7d983c80e0f537fc2f453aa2a4c485cc2c9d7 100644
--- a/pkg/compiler/lib/src/ssa/type_builder.dart
+++ b/pkg/compiler/lib/src/ssa/type_builder.dart
@@ -72,7 +72,7 @@ class TypeBuilder {
       {SourceInformation sourceInformation}) {
     assert(assertTypeInContext(type));
     if (type is MethodTypeVariableType) {
-      return builder.graph.addConstantNull(builder.compiler);
+      return builder.graph.addConstantNull(builder.closedWorld);
     }
     bool isClosure = member.enclosingElement.isClosure;
     if (isClosure) {
@@ -177,7 +177,7 @@ class TypeBuilder {
     argument = argument.unaliased;
     if (argument.treatAsDynamic) {
       // Represent [dynamic] as [null].
-      return builder.graph.addConstantNull(builder.compiler);
+      return builder.graph.addConstantNull(builder.closedWorld);
     }
 
     if (argument.isTypeVariable) {