[Print Preview] Re-add flags for register promos

chrome/common/chrome_switches.cc

Index: chrome/common/chrome_switches.cc
diff --git a/chrome/common/chrome_switches.cc b/chrome/common/chrome_switches.cc
index f3b33687a2fe7bb1ef22bc9b3c4d56a4a3a68856..21a52a81c3f1339378870c16447e17305878805a 100644
--- a/chrome/common/chrome_switches.cc
+++ b/chrome/common/chrome_switches.cc
@@ -711,6 +711,10 @@ const char kEnableOriginChipV2HideOnUserInput[] =
 // Enables panels (always on-top docked pop-up windows).
 const char kEnablePanels[]                  = "enable-panels";
 
+// Enables showing unregistered printers in print preview
+const char kEnablePrintPreviewRegisterPromos[] =
+    "enable-print-preview-register-promos";
+
 // Enable Privet storage.
 const char kEnablePrivetStorage[]     = "enable-privet-storage";