VM Propagate receiver type from calls to unique selectors in AOT compilation.

tests/language/vm/unique_selector_test.dart

+// Copyright (c) 2016, 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.
+
+import "package:expect/expect.dart";
+
+class A {
+  _unique_method() => "foo";
+  bar() => "A";
+}
+
+class B {
+  noSuchMethod(invocation) => "nsm";
+  bar() => "B";
+}
+
+confuse(x) {
+  try {
+    throw x;
+  } catch (e) {
+    return e;
+  }
+  return null;
+}
+
+main() {
+  var a = confuse(new A());
+  Expect.equals("foo", a._unique_method());
+  Expect.equals("A", a.bar());
+
+  var b = confuse(new B());
+  Expect.equals("nsm", b._unique_method());
+  Expect.equals("B", b.bar()); // Don't propagate type A to b.
+}