Connect mojom::DisplayController from ash to ui.

services/ui/display/platform_screen.h

Index: services/ui/display/platform_screen.h
diff --git a/services/ui/display/platform_screen.h b/services/ui/display/platform_screen.h
index 262334ed627eb8d1be03ca34e0ef282636ed3e13..a347a9718a2db4158396860e3e4ce9932c52e2e0 100644
--- a/services/ui/display/platform_screen.h
+++ b/services/ui/display/platform_screen.h
@@ -10,6 +10,10 @@
 #include "base/macros.h"
 #include "services/ui/display/platform_screen_delegate.h"
 
+namespace shell {
+class InterfaceRegistry;
+}
+
 namespace display {
 
 // PlatformScreen provides the necessary functionality to configure all
@@ -23,6 +27,9 @@ class PlatformScreen {
   static std::unique_ptr<PlatformScreen> Create();
   static PlatformScreen* GetInstance();
 
+  // Registers Mojo interfaces provided.
+  virtual void AddInterfaces(shell::InterfaceRegistry* registry) = 0;
+
   // Triggers initial display configuration to start. On device this will
   // configuration the connected displays. Off device this will create one or
   // more fake displays and pretend to configure them. A non-null |delegate|