Adds ability for ash_unittests to run in mushrome mode

ash/test/ash_test_helper.h

Index: ash/test/ash_test_helper.h
diff --git a/ash/test/ash_test_helper.h b/ash/test/ash_test_helper.h
index 4a8d42d8be5cf02b600672b6a6421c486708b936..70e3b8b96900a5b7b974aca353ac856fcc0adb77 100644
--- a/ash/test/ash_test_helper.h
+++ b/ash/test/ash_test_helper.h
@@ -25,6 +25,12 @@ namespace display {
 class Display;
 }
 
+namespace mash {
+namespace test {
+class MashTestSuite;
+}
+}
+
 namespace ui {
 class ScopedAnimationDurationScaleMode;
 }  // namespace ui
@@ -37,6 +43,8 @@ namespace ash {
 
 class RootWindowController;
 
+enum class Config;

[msw, 2017/03/30 23:06:05]

optional nit: order before RootWindowController?

[sky, 2017/03/30 23:35:46]

I actually prefer separating them out and there doesn't appear to be a standard
here...

+
 namespace mus {
 class WindowManagerApplication;
 }
@@ -44,6 +52,7 @@ class WindowManagerApplication;
 namespace test {
 
 class AshTestEnvironment;
+class AshTestSuite;

[msw, 2017/03/30 23:06:05]

optional nit: technically, I don't think this fwd decl is needed

 class AshTestViewsDelegate;
 class TestScreenshotDelegate;
 class TestShellDelegate;
@@ -103,6 +112,10 @@ class AshTestHelper {
   }
 
  private:
+  // The two TestSuites need to manipulate |config_|.

[msw, 2017/03/30 23:06:05]

nit: These? optionally expose |config_for_testing()| accessor instead?

[sky, 2017/03/30 23:35:46]

They need to set config_, which I would like to restrict to the TestSuites.

+  friend class AshTestSuite;
+  friend class mash::test::MashTestSuite;
+
   // Called when running in mash to create the WindowManager.
   void CreateMashWindowManager();
 
@@ -122,11 +135,13 @@ class AshTestHelper {
 
   std::vector<RootWindowController*> GetRootsOrderedByDisplayId();
 
+  static Config config_;
+
   AshTestEnvironment* ash_test_environment_;  // Not owned.
   TestShellDelegate* test_shell_delegate_;  // Owned by ash::Shell.
   std::unique_ptr<ui::ScopedAnimationDurationScaleMode> zero_duration_mode_;
 
-  // Owned by ash::AcceleratorController
+  // Owned by ash::AcceleratorController.
   TestScreenshotDelegate* test_screenshot_delegate_;
 
   std::unique_ptr<::wm::WMState> wm_state_;