Remove dart backend

test/dart_codegen/expect/collection/linked_hash_set.dart

Index: test/dart_codegen/expect/collection/linked_hash_set.dart
diff --git a/test/dart_codegen/expect/collection/linked_hash_set.dart b/test/dart_codegen/expect/collection/linked_hash_set.dart
deleted file mode 100644
index 420f87a53ef5c5757686305e21b3df5aff043a7e..0000000000000000000000000000000000000000
--- a/test/dart_codegen/expect/collection/linked_hash_set.dart
+++ /dev/null
@@ -1,15 +0,0 @@
-part of dart.collection;
- abstract class LinkedHashSet<E> implements HashSet<E> {external factory LinkedHashSet({
-  bool equals(E e1, E e2), int hashCode(E e), bool isValidKey(potentialKey)}
-);
- external factory LinkedHashSet.identity();
- factory LinkedHashSet.from(Iterable<E> elements) {
-  LinkedHashSet<E> result = new LinkedHashSet<E>();
-   for (final E element in elements) {
-    result.add(element);
-    }
-   return result;
-  }
- void forEach(void action(E element));
- Iterator<E> get iterator;
-}