[Sync] Persist keystore key across restarts

chrome/browser/sync/sync_prefs.h

Index: chrome/browser/sync/sync_prefs.h
diff --git a/chrome/browser/sync/sync_prefs.h b/chrome/browser/sync/sync_prefs.h
index cecd20865fb6f382bd511f0ff5c299dd6dbd8a60..a633be42e95e68ed03e287db4bd0c05698baa662 100644
--- a/chrome/browser/sync/sync_prefs.h
+++ b/chrome/browser/sync/sync_prefs.h
@@ -94,10 +94,15 @@ class SyncPrefs : public base::SupportsWeakPtr<SyncPrefs>,
   // This pref is set outside of sync.
   bool IsManaged() const;
 
-  // Use this encryption bootstrap token once already syncing.
+  // Use this encryption bootstrap token if we're using an explicit passphrase.
   std::string GetEncryptionBootstrapToken() const;
   void SetEncryptionBootstrapToken(const std::string& token);
 
+  // Use this keystore bootstrap token if we're not using an explicit
+  // passphrase.
+  std::string GetKeystoreEncryptionBootstrapToken() const;
+  void SetKeystoreEncryptionBootstrapToken(const std::string& token);
+
 #if defined(OS_CHROMEOS)
   // Use this spare bootstrap token only when setting up sync for the first
   // time.