Reland: mus: Add views_mus_interactive_ui_tests target

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 a415ff9ae860f1f5bca9635d2da8ac8a971a4507..1d309ee25931b11829d15dacd8a0ca940a59056c 100644
--- a/ui/views/test/platform_test_helper.cc
+++ b/ui/views/test/platform_test_helper.cc
@@ -17,13 +17,12 @@ class DefaultPlatformTestHelper : public PlatformTestHelper {
 
   ~DefaultPlatformTestHelper() override {}
 
-  bool IsMus() const override { return false; }
-
  private:
   DISALLOW_COPY_AND_ASSIGN(DefaultPlatformTestHelper);
 };
 
 PlatformTestHelper::Factory test_helper_factory;
+bool is_mus = false;
 
 }  // namespace
 
@@ -39,4 +38,14 @@ std::unique_ptr<PlatformTestHelper> PlatformTestHelper::Create() {
              : base::WrapUnique(new DefaultPlatformTestHelper);
 }
 
+// static
+void PlatformTestHelper::SetIsMus() {
+  is_mus = true;
+}
+
+// static
+bool PlatformTestHelper::IsMus() {
+  return is_mus;
+}
+
 }  // namespace views