Add KernelWorldBuilder and KElement model.

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

Index: pkg/compiler/lib/src/ssa/nodes.dart
diff --git a/pkg/compiler/lib/src/ssa/nodes.dart b/pkg/compiler/lib/src/ssa/nodes.dart
index b00668e06878e25c5de03698d6187b0bd9b28efc..e6a632dcf2b3d8e0241fb829982b6c35515adcf8 100644
--- a/pkg/compiler/lib/src/ssa/nodes.dart
+++ b/pkg/compiler/lib/src/ssa/nodes.dart
@@ -8,8 +8,7 @@ import '../common/backend_api.dart' show BackendClasses;
 import '../compiler.dart' show Compiler;
 import '../constants/constant_system.dart';
 import '../constants/values.dart';
-import '../elements/elements.dart'
-    show JumpTarget, LabelDefinition;
+import '../elements/elements.dart' show JumpTarget, LabelDefinition;
 import '../elements/entities.dart';
 import '../elements/types.dart';
 import '../io/source_information.dart';
@@ -1352,7 +1351,7 @@ abstract class HInstruction implements Spannable {
     assert(!type.isTypeVariable);
     assert(type.treatAsRaw || type.isFunctionType);
     if (type.isDynamic) return this;
-    if (type.isObject) return this;
+    if (type == closedWorld.commonElements.objectType) return this;
     if (type.isVoid || type.isFunctionType || type.isMalformed) {
       return new HTypeConversion(
           type, kind, closedWorld.commonMasks.dynamicType, this);