Remove prefs::kSyncSpareBootstrapToken which is never set

The pref was read by ProfileSyncService, but never actually set.

Bug: 938869
Change-Id: Ie924712e82f97c4c2459329e4830aa50e3cfc57d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1556795
Auto-Submit: Marc Treib <[email protected]>
Reviewed-by: Mohamed Amir Yosef <[email protected]>
Commit-Queue: Marc Treib <[email protected]>
Cr-Commit-Position: refs/heads/master@{#648617}
diff --git a/chrome/browser/prefs/browser_prefs.cc b/chrome/browser/prefs/browser_prefs.cc
index 796c1821..31e72753 100644
--- a/chrome/browser/prefs/browser_prefs.cc
+++ b/chrome/browser/prefs/browser_prefs.cc
@@ -1016,4 +1016,9 @@
   profile_prefs->ClearPref(kDismissedAssetDownloadSuggestions);
   profile_prefs->ClearPref(kDismissedOfflinePageDownloadSuggestions);
 #endif  // defined(OS_ANDROID)
+
+#if defined(OS_CHROMEOS)
+  // Added 4/2019.
+  syncer::ClearObsoleteSyncSpareBootstrapToken(profile_prefs);
+#endif  // defined(OS_CHROMEOS)
 }