[Sync] Persist keystore key across restarts

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 735255c55d702de6055a7a7d235f15c0d29b26ac..76c1badb82556067786ffb8e619a347a9e996cb9 100644
--- a/chrome/common/pref_names.cc
+++ b/chrome/common/pref_names.cc
@@ -1646,6 +1646,11 @@ const char kInvalidatorMaxInvalidationVersions[] =
 const char kSyncEncryptionBootstrapToken[] =
     "sync.encryption_bootstrap_token";
 
+// Same as kSyncEncryptionBootstrapToken, but derived from the keystore key,
+// so we don't have to do a GetKey command at restart.
+const char kSyncKeystoreEncryptionBootstrapToken[] =
+    "sync.keystore_encryption_bootstrap_token";
+
 // Boolean tracking whether the user chose to specify a secondary encryption
 // passphrase.
 const char kSyncUsingSecondaryPassphrase[] = "sync.using_secondary_passphrase";