views/mus: Install a mus-friend ContextFactory for tests.

ui/views/test/platform_test_helper.cc

Index: ui/views/test/platform_test_helper.cc
diff --git a/ui/views/test/platform_test_helper.cc b/ui/views/test/platform_test_helper.cc
index c6204abde63baed51cf57c37f4ad3fdb44632be7..0816cdf417c3e3f597e52612332897875995c855 100644
--- a/ui/views/test/platform_test_helper.cc
+++ b/ui/views/test/platform_test_helper.cc
@@ -7,6 +7,7 @@
 #include "base/callback.h"
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
+#include "ui/compositor/test/context_factories_for_test.h"
 #include "ui/views/widget/widget.h"
 
 #if defined(USE_AURA)
@@ -21,6 +22,10 @@ bool is_mus = false;
 
 }  // namespace
 
+PlatformTestHelper::~PlatformTestHelper() {
+  ui::TerminateContextFactoryForTests();
+}
+
 void PlatformTestHelper::set_factory(const Factory& factory) {
   DCHECK(test_helper_factory.is_null());
   test_helper_factory = factory;
@@ -49,4 +54,12 @@ void PlatformTestHelper::SimulateNativeDestroy(Widget* widget) {
 }
 #endif
 
+void PlatformTestHelper::InitializeContextFactory(
+    ui::ContextFactory** context_factory,
+    ui::ContextFactoryPrivate** context_factory_private) {
+  bool enable_pixel_output = false;
+  ui::InitializeContextFactoryForTests(enable_pixel_output, context_factory,
+                                       context_factory_private);
+}
+
 }  // namespace views