Implementing sign-in promo histograms for settings

ios/chrome/browser/pref_names.cc

Index: ios/chrome/browser/pref_names.cc
diff --git a/ios/chrome/browser/pref_names.cc b/ios/chrome/browser/pref_names.cc
index d87f47e38102d10041e90bf66977c5f8d7d97ff4..c1ae2c06a7d1f53d8e8f6d97be3511be8ab399a6 100644
--- a/ios/chrome/browser/pref_names.cc
+++ b/ios/chrome/browser/pref_names.cc
@@ -69,6 +69,11 @@ const char kIosBookmarkPromoAlreadySeen[] = "ios.bookmark.promo_already_seen";
 const char kIosBookmarkSigninPromoDisplayedCount[] =
     "ios.bookmark.signin_promo_displayed_count";
 
+// Integer to represent the number of time the sign-in promo has been displayed
+// in the settings view.
+const char kIosSettingsSigninPromoDisplayedCount[] =
+    "ios.settings.signin_promo_displayed_count";
+
 // Whether the user has enabled the Physical Web feature to surface URLs
 // broadcast by nearby devices.
 const char kIosPhysicalWebEnabled[] = "ios.physical_web_enabled";