Move kInvalidDisplayID to display_constants.h.

ui/display/fake_display_snapshot.cc

Index: ui/display/fake_display_snapshot.cc
diff --git a/ui/display/fake_display_snapshot.cc b/ui/display/fake_display_snapshot.cc
index 1471f5e16558d4eb65b02319d4aab2911e56a4df..e2c274f77bed5fd36b71826fd85988b48a7e14ec 100644
--- a/ui/display/fake_display_snapshot.cc
+++ b/ui/display/fake_display_snapshot.cc
@@ -183,7 +183,7 @@ Builder::Builder() {}
 Builder::~Builder() {}
 
 std::unique_ptr<FakeDisplaySnapshot> Builder::Build() {
-  if (modes_.empty() || id_ == Display::kInvalidDisplayID) {
+  if (modes_.empty() || id_ == kInvalidDisplayId) {
     NOTREACHED() << "Display modes or display ID missing";
     return nullptr;
   }