[debugger] be more lenient about argument type in %DebugGetProperty.

R=mstarzinger@chromium.org
BUG=chromium:629996

Review-Url: https://codereview.chromium.org/2166123003
Cr-Commit-Position: refs/heads/master@{#37942}

src/runtime/runtime-debug.cc

@@ -408,7 +408,7 @@ RUNTIME_FUNCTION(Runtime_DebugGetProperty) {
 
   DCHECK(args.length() == 2);
 
-  CONVERT_ARG_HANDLE_CHECKED(JSObject, obj, 0);
+  CONVERT_ARG_HANDLE_CHECKED(Object, obj, 0);
   CONVERT_ARG_HANDLE_CHECKED(Name, name, 1);
 
   LookupIterator it(obj, name);

test/mjsunit/regress/regress-crbug-629996.js

+// Copyright 2016 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 mirror = debug.MakeMirror(new Proxy({}, {}));
+// As long as we have no special mirror for proxies, we use an object mirror.
+assertEquals("object", mirror.type());