Fix a bug where we would emit a noSuchMethod handler in the Object class for Object methods because…

tests/language/abstract_exact_selector_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.
+
+// Regression test for dart2js that used to duplicate some `Object`
+// methods to handle `noSuchMethod`.
+
+import "package:expect/expect.dart";
+import "compiler_annotations.dart";
+
+abstract class Foo {
+  noSuchMethod(im) => 42;
+}
+
+@DontInline()
+returnFoo() {
+  (() => 42)();
+  return new Foo();
+}
+
+class Bar {
+  operator==(other) => false;
+}
+
+var a = [false, true, new Object(), new Bar()];
+
+main() {
+  if (a[0]) {
+    // This `==` call will make the compiler create a selector with an
+    // exact `TypeMask` of `Foo`. Since `Foo` is abstract, such a call
+    // cannot happen, but we still used to generate a `==` method on
+    // the `Object` class to handle `noSuchMethod`.
+    print(returnFoo() == 42);
+  } else {
+    Expect.isFalse(a[2] == 42);
+  }
+}