Add Mojo application test support to Chromium.

mojo/environment/default_run_loop_impl.cc

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "mojo/environment/default_run_loop_impl.h"
+
+#include "base/logging.h"
+#include "base/message_loop/message_loop.h"
+
+namespace mojo {
+namespace internal {
+
+void InstantiateDefaultRunLoopImpl() {
+  CHECK(!base::MessageLoop::current());

[jamesr, 2014/11/11 22:34:37]

there's already a DCHECK in MessageLoop that covers this, don't add a redundant
one

[msw, 2014/11/11 23:00:07]

Done.

+  // Not leaked: accessible from |base::MessageLoop::current()|.
+  base::MessageLoop* message_loop = new base::MessageLoop();
+  CHECK_EQ(message_loop, base::MessageLoop::current());

[jamesr, 2014/11/11 22:34:37]

this is over-checking. a post-condition of the MessageLoop constructor is that
it's in the current() slot

[msw, 2014/11/11 23:00:07]

Done.

+}
+
+void DestroyDefaultRunLoopImpl() {
+  CHECK(base::MessageLoop::current());

[jamesr, 2014/11/11 22:34:37]

ditto

[msw, 2014/11/11 23:00:07]

Done.

+  delete base::MessageLoop::current();

[jamesr, 2014/11/11 22:34:37]

this is icky. do you expect people to be calling this from multiple threads?
seems nicer to keep track of this ourselves

[msw, 2014/11/11 23:00:07]

For now, this is used by ApplicationTestBase and application_test_main's
MojoMain; I'm not sure what else might appreciate this environment abstraction.
I can probably remove them altogether if I split ApplicationTestBase into
chromium and standalone variants. I'll follow whatever you suggest.

+  CHECK(!base::MessageLoop::current());

[jamesr, 2014/11/11 22:34:37]

more over-checking

[msw, 2014/11/11 23:00:07]

Done.

+}
+
+}  // namespace internal
+}  // namespace mojo