Revert of Reland: mus: Add views_mus_interactive_ui_tests target

ui/views/test/platform_test_helper.h

Index: ui/views/test/platform_test_helper.h
diff --git a/ui/views/test/platform_test_helper.h b/ui/views/test/platform_test_helper.h
index 236446afac0b10aa93313824b918fc667f7c9b2f..2214270eaaa3a7bdb4f8d3cc22ad0850dff3c0dc 100644
--- a/ui/views/test/platform_test_helper.h
+++ b/ui/views/test/platform_test_helper.h
@@ -21,10 +21,7 @@
   static void set_factory(const Factory& factory);
   static std::unique_ptr<PlatformTestHelper> Create();
 
-  // Whether we are running under the mus environment. Methods are static so
-  // that they can be called before Create().
-  static void SetIsMus();
-  static bool IsMus();
+  virtual bool IsMus() const = 0;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(PlatformTestHelper);