Initial CL for Data Saver (Flywheel) prompt when cellular network detected

chrome/common/pref_names.cc

Index: chrome/common/pref_names.cc
diff --git a/chrome/common/pref_names.cc b/chrome/common/pref_names.cc
index 46cc10ae791a72e49fff875d8bf20e2705413c79..9b4d3d776e7c15259186c7ec53a6a2c7dbfccceb 100644
--- a/chrome/common/pref_names.cc
+++ b/chrome/common/pref_names.cc
@@ -610,6 +610,10 @@ const char kShowPlanNotifications[] =
 const char kShow3gPromoNotification[] =
     "settings.internet.mobile.show_3g_promo_notification";
 
+// An integer pref counting times Data Saver prompt has been shown.
+const char kDataSaverPromptsShown[] =
+    "settings.internet.mobile.datasaver_prompts_shown";
+
 // A string pref that contains version where "What's new" promo was shown.
 const char kChromeOSReleaseNotesVersion[] = "settings.release_notes.version";