[Sync] Remove backend unrecoverable error handler

sync/util/test_unrecoverable_error_handler.cc

 // Copyright (c) 2012 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/test_unrecoverable_error_handler.h"
 
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace syncer {
 
-TestUnrecoverableErrorHandler::TestUnrecoverableErrorHandler() {}
+TestUnrecoverableErrorHandler::TestUnrecoverableErrorHandler()
+    : weak_ptr_factory_(this) {}
 
 TestUnrecoverableErrorHandler::~TestUnrecoverableErrorHandler() {}
 
 void TestUnrecoverableErrorHandler::OnUnrecoverableError(
     const tracked_objects::Location& from_here,
     const std::string& message) {
   ADD_FAILURE_AT(from_here.file_name(), from_here.line_number())
       << from_here.function_name() << ": " << message;
 }
 
+base::WeakPtr<TestUnrecoverableErrorHandler>
+TestUnrecoverableErrorHandler::GetWeakPtr() {
+  return weak_ptr_factory_.GetWeakPtr();
+}
+
 }  // namespace syncer