[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 f6dd8a8f2995b81d059ecea396bb3387cc08df66..13366dab998066fc074883acc5b3d4da6cec9b40 100644
--- a/chrome/common/pref_names.cc
+++ b/chrome/common/pref_names.cc
@@ -1590,6 +1590,11 @@ const char kInvalidatorInvalidationState[] = "invalidator.invalidation_state";
 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";