Use entities in the TypeMask interface.

pkg/compiler/lib/src/types/forwarding_type_mask.dart

Index: pkg/compiler/lib/src/types/forwarding_type_mask.dart
diff --git a/pkg/compiler/lib/src/types/forwarding_type_mask.dart b/pkg/compiler/lib/src/types/forwarding_type_mask.dart
index 775fee0575e2e16b0fdb168018c028c642982904..73ac59d73b08f18d91981ae78c6c4bf43c26650e 100644
--- a/pkg/compiler/lib/src/types/forwarding_type_mask.dart
+++ b/pkg/compiler/lib/src/types/forwarding_type_mask.dart
@@ -97,11 +97,12 @@ abstract class ForwardingTypeMask implements TypeMask {
     return forwardTo.needsNoSuchMethodHandling(selector, closedWorld);
   }
 
-  bool canHit(Element element, Selector selector, ClosedWorld closedWorld) {
+  bool canHit(
+      MemberEntity element, Selector selector, ClosedWorld closedWorld) {
     return forwardTo.canHit(element, selector, closedWorld);
   }
 
-  Element locateSingleElement(Selector selector, ClosedWorld closedWorld) {
+  MemberEntity locateSingleElement(Selector selector, ClosedWorld closedWorld) {
     return forwardTo.locateSingleElement(selector, closedWorld);
   }