Implement rudimentary touchscreen support in mus.

components/mus/ws/platform_screen_impl_ozone.h

Index: components/mus/ws/platform_screen_impl_ozone.h
diff --git a/components/mus/ws/platform_screen_impl_ozone.h b/components/mus/ws/platform_screen_impl_ozone.h
index 22927de987e9db538c3c39a138418ad38b0803a9..55949e4b45c62e86b362478e919952329dcf86a4 100644
--- a/components/mus/ws/platform_screen_impl_ozone.h
+++ b/components/mus/ws/platform_screen_impl_ozone.h
@@ -51,6 +51,14 @@ class PlatformScreenImplOzone : public PlatformScreen,
   void OnDisplaysAquired(const ConfiguredDisplayCallback& callback,
                          const std::vector<ui::DisplaySnapshot*>& displays);
 
+  // The display subsystem calls |OnDisplayConfigured| for each display that has
+  // been successfully configured. This in turn calls |callback_| with the
+  // identity and bounds of each physical display.
+  void OnDisplayConfigured(const ConfiguredDisplayCallback& callback,
+                           int64_t id,
+                           const gfx::Rect& bounds,
+                           bool success);
+
   std::unique_ptr<ui::NativeDisplayDelegate> native_display_delegate_;
 
   base::WeakPtrFactory<PlatformScreenImplOzone> weak_ptr_factory_;