dart2js cps: Keep interceptors in a separate field.

pkg/compiler/lib/src/js_backend/codegen/glue.dart

Index: pkg/compiler/lib/src/js_backend/codegen/glue.dart
diff --git a/pkg/compiler/lib/src/js_backend/codegen/glue.dart b/pkg/compiler/lib/src/js_backend/codegen/glue.dart
index 46ef1a55726e54bff1e66cd449523faf111ae878..abbb894fd1fbc9291cb4d47cfc54589830604696 100644
--- a/pkg/compiler/lib/src/js_backend/codegen/glue.dart
+++ b/pkg/compiler/lib/src/js_backend/codegen/glue.dart
@@ -299,4 +299,10 @@ class Glue {
   bool mayGenerateInstanceofCheck(DartType type) {
     return _backend.mayGenerateInstanceofCheck(type);
   }
+
+  bool methodUsesReceiverArgument(FunctionElement function) {
+    assert(isInterceptedMethod(function));
+    ClassElement class_ = function.enclosingClass.declaration;
+    return isInterceptorClass(class_) || isUsedAsMixin(class_);
+  }
 }