Rename Constant to ConstantValue and ConstExp to ConstantExpression.

sdk/lib/_internal/compiler/implementation/use_unused_api.dart

Index: sdk/lib/_internal/compiler/implementation/use_unused_api.dart
diff --git a/sdk/lib/_internal/compiler/implementation/use_unused_api.dart b/sdk/lib/_internal/compiler/implementation/use_unused_api.dart
index ad196350e520addd1996ff8c6f3aaf2357621d78..d4a270e34cf42ae11c3044aa6a373cfe34d19155 100644
--- a/sdk/lib/_internal/compiler/implementation/use_unused_api.dart
+++ b/sdk/lib/_internal/compiler/implementation/use_unused_api.dart
@@ -64,7 +64,8 @@ useApi() {
   api.ReadStringFromUri uri;
 }
 
-void useConstant(constants.Constant constant, dart2jslib.ConstantSystem cs) {
+void useConstant(constants.ConstantValue constant,
+                 dart2jslib.ConstantSystem cs) {
   constant.isObject;
   cs.isBool(constant);
 }