Move kInvalidDisplayID to display_constants.h.

ui/display/display.h

Index: ui/display/display.h
diff --git a/ui/display/display.h b/ui/display/display.h
index 24949393e243ac28da6d7f4e201f53eafa19e8b6..1a8ebcf42ddb43bfb469205582f8e87fc4713a85 100644
--- a/ui/display/display.h
+++ b/ui/display/display.h
@@ -9,6 +9,7 @@
 
 #include "base/compiler_specific.h"
 #include "ui/display/display_export.h"
+#include "ui/display/types/display_constants.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/icc_profile.h"
 
@@ -65,9 +66,11 @@ class DISPLAY_EXPORT Display final {
     TOUCH_SUPPORT_UNAVAILABLE,
   };
 
-  enum : int64_t { kInvalidDisplayID = -1 };
+  // Use display::kInvalidDisplayId from display_constants.h in new code.
+  // TODO(kylechar): Delete after all references are gone.
+  enum : int64_t { kInvalidDisplayID = display::kInvalidDisplayId };
 
-  // Creates a display with kInvalidDisplayID as default.
+  // Creates a display with kInvalidDisplayId as default.
   Display();
   explicit Display(int64_t id);
   Display(int64_t id, const gfx::Rect& bounds);
@@ -144,7 +147,7 @@ class DISPLAY_EXPORT Display final {
   std::string ToString() const;
 
   // True if the display contains valid display id.
-  bool is_valid() const { return id_ != kInvalidDisplayID; }
+  bool is_valid() const { return id_ != kInvalidDisplayId; }
 
   // True if the display corresponds to internal panel.
   bool IsInternal() const;