Add CoreClasses

pkg/compiler/lib/src/js_emitter/startup_emitter/fragment_emitter.dart

Index: pkg/compiler/lib/src/js_emitter/startup_emitter/fragment_emitter.dart
diff --git a/pkg/compiler/lib/src/js_emitter/startup_emitter/fragment_emitter.dart b/pkg/compiler/lib/src/js_emitter/startup_emitter/fragment_emitter.dart
index c8e6a755167b5c55b45b9ef199d2a0d0ea900208..7fbd768820923fa63483f2f4c8995a5a128d231a 100644
--- a/pkg/compiler/lib/src/js_emitter/startup_emitter/fragment_emitter.dart
+++ b/pkg/compiler/lib/src/js_emitter/startup_emitter/fragment_emitter.dart
@@ -1091,12 +1091,13 @@ class FragmentEmitter {
   js.Property emitMangledGlobalNames() {
     List<js.Property> names = <js.Property>[];
 
+    CoreClasses coreClasses = compiler.coreClasses;
     // We want to keep the original names for the most common core classes when
     // calling toString on them.
     List<ClassElement> nativeClassesNeedingUnmangledName =
-        [compiler.intClass, compiler.doubleClass, compiler.numClass,
-         compiler.stringClass, compiler.boolClass, compiler.nullClass,
-         compiler.listClass];
+        [coreClasses.intClass, coreClasses.doubleClass, coreClasses.numClass,
+          coreClasses.stringClass, coreClasses.boolClass, coreClasses.nullClass,
+          coreClasses.listClass];
     // TODO(floitsch): this should probably be on a per-fragment basis.
     nativeClassesNeedingUnmangledName.forEach((element) {
       names.add(new js.Property(js.quoteName(namer.className(element)),