Stop creating selectors in the SSA builder that were already created by the resolver.

tests/language/super_operator_index_test.dart

+// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// Test that we emit warnings for unresolved indexing operations on super.
+
+class A {
+  operator[]=(a, b) {}
+}
+
+class B extends A {
+  foo() {
+    super[4] = 42;
+    super[4] += 5; /// 01: static type warning, runtime error
+    return super[2]; /// 02: static type warning, runtime error
+  }
+}
+
+class C {
+  operator[](a) {}
+}
+
+class D extends C {
+  foo() {
+    super[4] = 42; /// 03: static type warning, runtime error
+    super[4] += 5; /// 04: static type warning, runtime error
+    return super[2];
+  }
+}
+
+class E {
+  foo() {
+    super[4] = 42; /// 05: static type warning, runtime error
+    super[4] += 5; /// 06: static type warning, runtime error
+    return super[2]; /// 07: static type warning, runtime error
+  }
+}
+
+main() {
+  new B().foo();
+  new D().foo();
+  new E().foo();
+}