Add kind to ConstantValue.

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

Index: pkg/compiler/lib/src/js_backend/namer.dart
diff --git a/pkg/compiler/lib/src/js_backend/namer.dart b/pkg/compiler/lib/src/js_backend/namer.dart
index aeea76eb4a145aaa23f17924d5b369a95ed19816..3a3811d58962c053689ffdeac0263ab16746b211 100644
--- a/pkg/compiler/lib/src/js_backend/namer.dart
+++ b/pkg/compiler/lib/src/js_backend/namer.dart
@@ -1768,7 +1768,7 @@ class ConstantNamingVisitor implements ConstantValueVisitor {
 
   @override
   void visitSynthetic(SyntheticConstantValue constant, [_]) {
-    switch (constant.kind) {
+    switch (constant.valueKind) {
       case SyntheticConstantKind.DUMMY_INTERCEPTOR:
         add('dummy_receiver');
         break;
@@ -1888,7 +1888,7 @@ class ConstantCanonicalHasher implements ConstantValueVisitor<int, Null> {
 
   @override
   int visitSynthetic(SyntheticConstantValue constant, [_]) {
-    switch (constant.kind) {
+    switch (constant.valueKind) {
       case SyntheticConstantKind.TYPEVARIABLE_REFERENCE:
         // These contain a deferred opaque index into metadata. There is nothing
         // we can access that is stable between compiles.  Luckily, since they