Check equivalence of closed world based on kernel elements.

pkg/compiler/lib/src/world.dart

Index: pkg/compiler/lib/src/world.dart
diff --git a/pkg/compiler/lib/src/world.dart b/pkg/compiler/lib/src/world.dart
index 59ee9b2561449c8f930f39ef2d16a53ffa31baee..6928f7dda7fe402bb836ff7e787bef8e0c20ba94 100644
--- a/pkg/compiler/lib/src/world.dart
+++ b/pkg/compiler/lib/src/world.dart
@@ -1100,6 +1100,20 @@ abstract class ClosedWorldBase implements ClosedWorld, ClosedWorldRefiner {
   bool getCurrentlyKnownMightBePassedToApply(Entity element) {
     return getMightBePassedToApply(element);
   }
+
+  // TODO(johnniwinther): Support [cls] as a [ClassEntity].
+  @override
+  String dump([ClassElement cls]) {
+    StringBuffer sb = new StringBuffer();
+    if (cls != null) {
+      sb.write("Classes in the closed world related to $cls:\n");
+    } else {
+      sb.write("Instantiated classes in the closed world:\n");
+    }
+    getClassHierarchyNode(commonElements.objectClass)
+        .printOn(sb, ' ', instantiatedOnly: cls == null, withRespectTo: cls);
+    return sb.toString();
+  }
 }
 
 class ClosedWorldImpl extends ClosedWorldBase {
@@ -1235,19 +1249,6 @@ class ClosedWorldImpl extends ClosedWorldBase {
     }
   }
 
-  @override
-  String dump([ClassElement cls]) {
-    StringBuffer sb = new StringBuffer();
-    if (cls != null) {
-      sb.write("Classes in the closed world related to $cls:\n");
-    } else {
-      sb.write("Instantiated classes in the closed world:\n");
-    }
-    getClassHierarchyNode(commonElements.objectClass)
-        .printOn(sb, ' ', instantiatedOnly: cls == null, withRespectTo: cls);
-    return sb.toString();
-  }
-
   SideEffects getSideEffectsOfElement(Element element) {
     // The type inferrer (where the side effects are being computed),
     // does not see generative constructor bodies because they are
@@ -1341,11 +1342,6 @@ class KernelClosedWorld extends ClosedWorldBase {
   }
 
   @override
-  String dump([ClassEntity cls]) {
-    throw new UnimplementedError('KernelClosedWorld.dump');
-  }
-
-  @override
   bool hasElementIn(ClassEntity cls, Selector selector, Entity element) {
     throw new UnimplementedError('KernelClosedWorld.hasElementIn');
   }