Add regression test for resolving "this" in debug evaluate.

test/mjsunit/regress/regress-crbug-487289.js

+// Copyright 2015 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --expose-debug-as debug
+
+var Debug = debug.Debug;
+var receiver = null;
+
+Debug.setListener(function(event, exec_state, event_data, data) {
+  if (event != Debug.DebugEvent.Break) return;
+  receiver = exec_state.frame(0).evaluate('this').value();
+});
+
+function f() { debugger; }
+
+var expected = {};
+f.call(expected);
+
+assertEquals(expected, receiver);