[views-mus] Prevent creating a native OzonePlatform in mus tests.

ui/views/test/widget_test_unittest.cc

Index: ui/views/test/widget_test_unittest.cc
diff --git a/ui/views/test/widget_test_unittest.cc b/ui/views/test/widget_test_unittest.cc
index 05f8c1d770aa541a1345b7f414d51b1a9489048c..90fbde1da50ae26061414c8b61ebb3d4f35d53bd 100644
--- a/ui/views/test/widget_test_unittest.cc
+++ b/ui/views/test/widget_test_unittest.cc
@@ -46,6 +46,11 @@ using WidgetTestTest = WidgetTest;
 // Ensure that Widgets with various root windows are correctly reported by
 // WidgetTest::GetAllWidgets().
 TEST_F(WidgetTestTest, GetAllWidgets) {
+  // TODO: this test transitively uses GetContext(). That should go away for
+  // aura-mus client. http://crbug.com/663781.
+  if (IsMus())
+    return;
+
   // Note Widget::Widgets is a std::set ordered by pointer value, so the order
   // that |expected| is updated below is not important.
   Widget::Widgets expected;