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..b1f9770201036a4f8951376c2fac5ea054a697e0 100644
--- a/ui/aura/test/aura_mus_test_base.cc
+++ b/ui/aura/test/aura_mus_test_base.cc
@@ -12,8 +12,20 @@ AuraMusWmTestBase::AuraMusWmTestBase() {}
 AuraMusWmTestBase::~AuraMusWmTestBase() {}
 
 void AuraMusWmTestBase::SetUp() {
+  // Run AuraTestBase::SetUp() first because it puts an InProcessContextFactory
+  // in env.
   EnableMusWithTestWindowTree();
   AuraTestBase::SetUp();
+
+  aura::Env* env = aura::Env::GetInstance();
+  DCHECK(env);
+  context_factory_to_restore_ = env->context_factory();
+  env->set_context_factory(&context_factory_);
+}
+
+void AuraMusWmTestBase::TearDown() {
+  aura::Env::GetInstance()->set_context_factory(context_factory_to_restore_);
+  AuraTestBase::TearDown();
 }
 
 AuraMusClientTestBase::AuraMusClientTestBase() {}
@@ -21,9 +33,21 @@ AuraMusClientTestBase::AuraMusClientTestBase() {}
 AuraMusClientTestBase::~AuraMusClientTestBase() {}
 
 void AuraMusClientTestBase::SetUp() {
+  // Run AuraTestBase::SetUp() first because it puts an InProcessContextFactory
+  // in env.
   EnableMusWithTestWindowTree();
   set_window_manager_delegate(nullptr);
   AuraTestBase::SetUp();
+
+  aura::Env* env = aura::Env::GetInstance();
+  DCHECK(env);
+  context_factory_to_restore_ = env->context_factory();
+  env->set_context_factory(&context_factory_);
+}
+
+void AuraMusClientTestBase::TearDown() {
+  aura::Env::GetInstance()->set_context_factory(context_factory_to_restore_);
+  AuraTestBase::TearDown();
 }
 
 }  // namespace test