Pass data objects to ConstantEmitter

pkg/compiler/lib/src/common_elements.dart

Index: pkg/compiler/lib/src/common_elements.dart
diff --git a/pkg/compiler/lib/src/common_elements.dart b/pkg/compiler/lib/src/common_elements.dart
index 46827ec543f3e1615bd4932d3648eacb502b0096..64d71fd199ea4684a479eedcf0a6218cd31abce4 100644
--- a/pkg/compiler/lib/src/common_elements.dart
+++ b/pkg/compiler/lib/src/common_elements.dart
@@ -739,6 +739,10 @@ class CommonElements {
   FunctionEntity get jsStringOperatorAdd =>
       _jsStringOperatorAdd ??= _findClassMember(jsStringClass, '+');
 
+  ClassEntity _jsConstClass;
+  ClassEntity get jsConstClass =>
+      _jsConstClass ??= _findClass(foreignLibrary, 'JS_CONST');
+
   // From package:js
   ClassEntity _jsAnnotationClass;
   ClassEntity get jsAnnotationClass {