Re-land "Issue 191223007: Move touch CTM from X into Chrome"

ash/host/ash_window_tree_host.h

Index: ash/host/ash_window_tree_host.h
diff --git a/ash/host/ash_window_tree_host.h b/ash/host/ash_window_tree_host.h
index d54813b24f8c806d498b24e790d4102b63d1e970..00626dba18435fb5a4c2249728637a229dcd24d7 100644
--- a/ash/host/ash_window_tree_host.h
+++ b/ash/host/ash_window_tree_host.h
@@ -45,6 +45,13 @@ class ASH_EXPORT AshWindowTreeHost {
   virtual gfx::Insets GetHostInsets() const = 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