mash: Migrate [Keyboard]Brightness code to ash/common.

ash/test/ash_test_base.h

Index: ash/test/ash_test_base.h
diff --git a/ash/test/ash_test_base.h b/ash/test/ash_test_base.h
index a02ec9d388bb8b2dab61ec6d423609fdef1e0f35..79a1c28f037d96a9e2ebe4029299fbf0726da366 100644
--- a/ash/test/ash_test_base.h
+++ b/ash/test/ash_test_base.h
@@ -41,6 +41,7 @@ class WindowDelegate;
 }  // namespace aura
 
 namespace ash {
+class BrightnessControlDelegate;
 class DisplayManager;
 class SystemTray;
 class WmShelf;
@@ -153,6 +154,9 @@ class AshTestBase : public testing::Test {
 
   void DisableIME();
 
+  void SetBrightnessControlDelegate(

[James Cook, 2016/07/07 23:08:50]

Yeah, I'd prefer to friend the test or tests if there are only going to be a
couple places that need it.

[msw, 2016/07/08 01:40:48]

Done.

+      std::unique_ptr<BrightnessControlDelegate> brightness_control_delegate);
+
  private:
   bool setup_called_;
   bool teardown_called_;