Add ConstantExpression.evaluate.

pkg/compiler/lib/src/js_backend/constant_handler_javascript.dart

Index: pkg/compiler/lib/src/js_backend/constant_handler_javascript.dart
diff --git a/pkg/compiler/lib/src/js_backend/constant_handler_javascript.dart b/pkg/compiler/lib/src/js_backend/constant_handler_javascript.dart
index 4771a5bc6e44f27c3d9370cb97b5a89a27d675bb..5f2cab828f9ce68fc8c185a501f05702cbb1df9c 100644
--- a/pkg/compiler/lib/src/js_backend/constant_handler_javascript.dart
+++ b/pkg/compiler/lib/src/js_backend/constant_handler_javascript.dart
@@ -203,14 +203,6 @@ class JavaScriptConstantCompiler extends ConstantCompilerBase
     return constant;
   }
 
-  ConstantExpression createTypeConstant(TypeDeclarationElement element) {
-    DartType elementType = element.rawType;
-    DartType constantType =
-        compiler.backend.typeImplementation.computeType(compiler);
-    return new TypeConstantExpression(
-        new TypeConstantValue(elementType, constantType), elementType);
-  }
-
   void forgetElement(Element element) {
     super.forgetElement(element);
     const ForgetConstantElementVisitor().visit(element, this);