Add an action for server to send down rollback command.

sync/protocol/sync_protocol_error.cc

Index: sync/protocol/sync_protocol_error.cc
diff --git a/sync/protocol/sync_protocol_error.cc b/sync/protocol/sync_protocol_error.cc
index cd22e9a46f600537df04ba33d6d49e434bd485b1..ac9e2fd658f2023b86feb74a00d4503afca62ca7 100644
--- a/sync/protocol/sync_protocol_error.cc
+++ b/sync/protocol/sync_protocol_error.cc
@@ -23,6 +23,7 @@ const char* GetSyncErrorTypeString(SyncProtocolErrorType type) {
     ENUM_CASE(MIGRATION_DONE);
     ENUM_CASE(INVALID_CREDENTIAL);
     ENUM_CASE(DISABLED_BY_ADMIN);
+    ENUM_CASE(USER_ROLLBACK);
     ENUM_CASE(UNKNOWN_ERROR);
   }
   NOTREACHED();
@@ -37,6 +38,7 @@ const char* GetClientActionString(ClientAction action) {
     ENUM_CASE(STOP_AND_RESTART_SYNC);
     ENUM_CASE(DISABLE_SYNC_ON_CLIENT);
     ENUM_CASE(STOP_SYNC_FOR_DISABLED_ACCOUNT);
+    ENUM_CASE(DISABLE_SYNC_AND_ROLLBACK);
     ENUM_CASE(UNKNOWN_ACTION);
   }
   NOTREACHED();