Revert of [Sync] Erase sync DB when corrupted

sync/util/mock_unrecoverable_error_handler.h

-// 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.
-
-#ifndef SYNC_UTIL_MOCK_UNRECOVERABLE_ERROR_HANDLER_H_
-#define SYNC_UTIL_MOCK_UNRECOVERABLE_ERROR_HANDLER_H_
-
-#include <string>
-
-#include "base/macros.h"
-#include "sync/internal_api/public/util/unrecoverable_error_handler.h"
-
-namespace syncer {
-
-// Mock implementation of UnrecoverableErrorHandler that counts how many times
-// it has been invoked.
-class MockUnrecoverableErrorHandler : public UnrecoverableErrorHandler {
- public:
-  MockUnrecoverableErrorHandler();
-  ~MockUnrecoverableErrorHandler() override;
-  void OnUnrecoverableError(const tracked_objects::Location& from_here,
-                            const std::string& message) override;
-
-  // Returns the number of times this handler has been invoked.
-  int invocation_count() const;
-
- private:
-  int invocation_count_;
-
-  DISALLOW_COPY_AND_ASSIGN(MockUnrecoverableErrorHandler);
-};
-
-}  // namespace syncer
-
-#endif  // SYNC_UTIL_MOCK_UNRECOVERABLE_ERROR_HANDLER_H_