Install FakeContextFactory for AuraMusWmTestBase

ui/aura/test/aura_mus_test_base.cc

Index: ui/aura/test/aura_mus_test_base.cc
diff --git a/ui/aura/test/aura_mus_test_base.cc b/ui/aura/test/aura_mus_test_base.cc
index e89b1eb458428c6b4da8e02f7305ed08309058c9..8cd4a8f03c0e531c76b1513c74712d4b2c436372 100644
--- a/ui/aura/test/aura_mus_test_base.cc
+++ b/ui/aura/test/aura_mus_test_base.cc
@@ -14,6 +14,16 @@ 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() {}