Optimize subclass/subtype queries

pkg/compiler/lib/src/elements/modelx.dart

Index: pkg/compiler/lib/src/elements/modelx.dart
diff --git a/pkg/compiler/lib/src/elements/modelx.dart b/pkg/compiler/lib/src/elements/modelx.dart
index 550b3c9396902d647a5af4eff1adff1efbccd31c..3f0d70ccab257c5f6f3694efbdd73a1346b78409 100644
--- a/pkg/compiler/lib/src/elements/modelx.dart
+++ b/pkg/compiler/lib/src/elements/modelx.dart
@@ -13,6 +13,8 @@ import '../compiler.dart' show
 import '../constants/constant_constructors.dart';
 import '../constants/constructors.dart';
 import '../constants/expressions.dart';
+import '../core_types.dart' show
+    CoreClasses;
 import '../dart_types.dart';
 import '../diagnostics/messages.dart' show
     MessageTemplate;
@@ -2706,8 +2708,8 @@ abstract class BaseClassElementX extends ElementX
     backendMembers.forEach(f);
   }
 
-  bool implementsFunction(Compiler compiler) {
-    return asInstanceOf(compiler.coreClasses.functionClass) != null ||
+  bool implementsFunction(CoreClasses coreClasses) {
+    return asInstanceOf(coreClasses.functionClass) != null ||
         callType != null;
   }