mus: Add views_mus_interactive_ui_tests target

ui/views/test/default_platform_test_helper.cc

Index: ui/views/test/default_platform_test_helper.cc
diff --git a/ui/views/test/default_platform_test_helper.cc b/ui/views/test/default_platform_test_helper.cc
index 8d498767e72355315831bb10abefca4da70da98a..728cb6c7ae0d1f528aa4a00c73f1c483f237e128 100644
--- a/ui/views/test/default_platform_test_helper.cc
+++ b/ui/views/test/default_platform_test_helper.cc
@@ -14,8 +14,6 @@ class DefaultPlatformTestHelper : public PlatformTestHelper {
 
   ~DefaultPlatformTestHelper() override {}
 
-  bool IsMus() const override { return false; }
-
  private:
   DISALLOW_COPY_AND_ASSIGN(DefaultPlatformTestHelper);
 };
@@ -27,4 +25,9 @@ std::unique_ptr<PlatformTestHelper> PlatformTestHelper::Create() {
   return base::WrapUnique(new DefaultPlatformTestHelper);
 }
 
+// static
+bool PlatformTestHelper::IsMus() {
+  return false;
+}
+
 }  // namespace views