Global handle leak in Realm.create() fixed.

BUG=chromium:501808
LOG=N

Review URL: https://codereview.chromium.org/1197403002

Cr-Commit-Position: refs/heads/master@{#29224}

src/d8.cc

@@ -496,6 +496,7 @@ void Shell::RealmCreate(const v8::FunctionCallbackInfo<v8::Value>& args) {
   data->realms_ = new Persistent<Context>[++data->realm_count_];
   for (int i = 0; i < index; ++i) {
     data->realms_[i].Reset(isolate, old_realms[i]);
+    old_realms[i].Reset();
   }
   delete[] old_realms;
   Handle<ObjectTemplate> global_template = CreateGlobalTemplate(isolate);

test/mjsunit/regress/regress-crbug-501808.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.
+
+var r = Realm.create();
+assertEquals(0, "a".localeCompare("a"));