Use entities in TypeVariableResolutionAnalysis and TypeVariableCodegenAnalysis

pkg/compiler/lib/src/kernel/world_builder.dart

Index: pkg/compiler/lib/src/kernel/world_builder.dart
diff --git a/pkg/compiler/lib/src/kernel/world_builder.dart b/pkg/compiler/lib/src/kernel/world_builder.dart
index 7713ae1c0b15a3ea1d169262648281156359850c..e86e06ce95e45eecf86dec77c4be544c34446e8c 100644
--- a/pkg/compiler/lib/src/kernel/world_builder.dart
+++ b/pkg/compiler/lib/src/kernel/world_builder.dart
@@ -559,6 +559,12 @@ class KernelElementEnvironment implements ElementEnvironment {
   }
 
   @override
+  DartType getTypeVariableBound(TypeVariableEntity typeVariable) {
+    throw new UnimplementedError(
+        'KernelElementEnvironment.getTypeVariableBound');
+  }
+
+  @override
   InterfaceType createInterfaceType(
       ClassEntity cls, List<DartType> typeArguments) {
     return new InterfaceType(cls, typeArguments);