Install FakeContextFactory for AuraMusWmTestBase

ui/aura/test/aura_mus_test_base.cc

 // Copyright 2016 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 "ui/aura/test/aura_mus_test_base.h"
 
 namespace aura {
 namespace test {
 
 AuraMusWmTestBase::AuraMusWmTestBase() {}
 
 AuraMusWmTestBase::~AuraMusWmTestBase() {}
 
 void AuraMusWmTestBase::SetUp() {
   EnableMusWithTestWindowTree();
   AuraTestBase::SetUp();
+
+  aura::Env* env = aura::Env::GetInstance();
+  DCHECK(env);
+  context_factory_to_restore_ = env->context_factory();
+  env->set_context_factory(&context_factory_);

[sadrul, 2017/05/04 17:50:46]

I think you want to do this first, before seeing up AuraTestBase?

[Alex Z., 2017/05/04 18:01:16]

AuraTestBase::SetUp() create an InProcessContextFactory and put it into env:
https://cs.chromium.org/chromium/src/ui/aura/test/aura_test_base.cc?l=83. If we
swap ContextFactory
before calling AuraTestBase, it gets overwritten.

[Alex Z., 2017/05/05 13:34:44]

I added a comment explaining this here.

+}
+
+void AuraMusWmTestBase::TearDown() {
+  aura::Env::GetInstance()->set_context_factory(context_factory_to_restore_);
+  AuraTestBase::TearDown();
 }
 
 AuraMusClientTestBase::AuraMusClientTestBase() {}
 
 AuraMusClientTestBase::~AuraMusClientTestBase() {}
 
 void AuraMusClientTestBase::SetUp() {
   EnableMusWithTestWindowTree();
   set_window_manager_delegate(nullptr);

[sadrul, 2017/05/04 17:50:46]

I think we should do this here too.

[Alex Z., 2017/05/04 18:01:16]

All aura_unittests passed without changing AuraMusClientTestBase. Do you still
want to do it here?

[Alex Z., 2017/05/05 13:34:44]

Done.

   AuraTestBase::SetUp();
 }
 
 }  // namespace test
 }  // namespace aura