Revert "Remove SendResolver.computeSendStructure."

pkg/compiler/lib/src/inferrer/simple_types_inferrer.dart

Index: pkg/compiler/lib/src/inferrer/simple_types_inferrer.dart
diff --git a/pkg/compiler/lib/src/inferrer/simple_types_inferrer.dart b/pkg/compiler/lib/src/inferrer/simple_types_inferrer.dart
index 5197d5bfbe3e5314a7f33fd62f38502056227360..42cb1865b31f3f98881a2c53c5f46dd5ecb90ad8 100644
--- a/pkg/compiler/lib/src/inferrer/simple_types_inferrer.dart
+++ b/pkg/compiler/lib/src/inferrer/simple_types_inferrer.dart
@@ -850,12 +850,9 @@ class SimpleTypeInferrerVisitor<T>
         isCallOnThis = true;
       }
     } else {
-      if (node.receiver != null) {
-        Element receiver = elements[node.receiver];
-        if (receiver is! PrefixElement && receiver is! ClassElement) {
-          // TODO(johnniwinther): Avoid blindly recursing on the receiver.
-          receiverType = visit(node.receiver);
-        }
+      if (node.receiver != null && elements[node.receiver] is! PrefixElement) {
+        // TODO(johnniwinther): Avoid blindly recursing on the receiver.
+        receiverType = visit(node.receiver);
       }
       isCallOnThis = isThisOrSuper(node.receiver);
     }