Merge 270252 "Re-land "Move touch CTM from X into Chrome""

ash/host/ash_window_tree_host.h

Index: ash/host/ash_window_tree_host.h
===================================================================
--- ash/host/ash_window_tree_host.h	(revision 271938)
+++ ash/host/ash_window_tree_host.h	(working copy)
@@ -42,6 +42,13 @@
       scoped_ptr<RootWindowTransformer> transformer) = 0;
 
   virtual aura::WindowTreeHost* AsWindowTreeHost() = 0;
+
+  // Updates the display IDs associated with this root window.
+  // A root window can be associated with up to 2 display IDs (e.g. in mirror
+  // mode dual monitors case). If the root window is only associated with one
+  // display id, then the other id should be set to
+  // gfx::Display::kInvalidDisplayID.
+  virtual void UpdateDisplayID(int64 id1, int64 id2) {};
 };
 
 }  // namespace ash