Add ConstantExpression.evaluate.

pkg/compiler/lib/src/use_unused_api.dart

Index: pkg/compiler/lib/src/use_unused_api.dart
diff --git a/pkg/compiler/lib/src/use_unused_api.dart b/pkg/compiler/lib/src/use_unused_api.dart
index 62c1fcb820dc8e40a959117e9551e1318ed5a732..ba59e6d54b198a7754e4128f5031f20a8aebb5ce 100644
--- a/pkg/compiler/lib/src/use_unused_api.dart
+++ b/pkg/compiler/lib/src/use_unused_api.dart
@@ -52,7 +52,7 @@ void main(List<String> arguments) {
   useApi();
   dart2js.main(arguments);
   dart2jslib.isPublicName(null);
-  useConstant(null, null, null);
+  useConstant(null, null, null, null, null);
   useNode(null);
   useUtil(null);
   useSetlet(null);
@@ -85,12 +85,16 @@ useApi() {
 }
 
 void useConstant(constants.ConstantValue constant,
+                 constants.ConstantExpression expression,
                  constants.ConstructedConstantExpression constructedConstant,
-                 constants.ConstantSystem cs) {
+                 constants.ConstantSystem cs,
+                 constants.Environment env) {
+
   constant.isObject;
   cs.isBool(constant);
   constructedConstant.computeInstanceType();
   constructedConstant.computeInstanceFields();
+  expression.evaluate(null, null);
 }
 
 void useNode(tree.Node node) {