mus: Introduce high-contrast mode in mus.

services/ui/ws/window_server.h

Index: services/ui/ws/window_server.h
diff --git a/services/ui/ws/window_server.h b/services/ui/ws/window_server.h
index 64e421169c6de0173a9972a0a990ae575e5b6df7..27934bb166007599238250c1f2be50d781d1c9c8 100644
--- a/services/ui/ws/window_server.h
+++ b/services/ui/ws/window_server.h
@@ -143,6 +143,9 @@ class WindowServer : public ServerWindowDelegate,
   bool SetFocusedWindow(ServerWindow* window);
   ServerWindow* GetFocusedWindow();
 
+  bool is_in_high_contrast_mode() const { return is_in_high_contrast_mode_; }
+  void SetHighContrastMode(bool enabled);
+
   // Returns a change id for the window manager that is associated with
   // |source| and |client_change_id|. When the window manager replies
   // WindowManagerChangeCompleted() is called to obtain the original source
@@ -333,6 +336,7 @@ class WindowServer : public ServerWindowDelegate,
   Operation* current_operation_;
 
   bool in_destructor_;
+  bool is_in_high_contrast_mode_ = false;
 
   // Maps from window manager change id to the client that initiated the
   // request.