Revert of [Sync] Erase sync DB when corrupted

sync/util/mock_unrecoverable_error_handler.cc

-// Copyright 2015 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#include "sync/util/mock_unrecoverable_error_handler.h"
-
-namespace syncer {
-
-MockUnrecoverableErrorHandler::MockUnrecoverableErrorHandler()
-    : invocation_count_(0) {
-}
-
-MockUnrecoverableErrorHandler::~MockUnrecoverableErrorHandler() {
-}
-
-void MockUnrecoverableErrorHandler::OnUnrecoverableError(
-    const tracked_objects::Location& from_here,
-    const std::string& message) {
-  ++invocation_count_;
-}
-
-int MockUnrecoverableErrorHandler::invocation_count() const {
-  return invocation_count_;
-}
-
-}  // namespace syncer