Delete invalidator.cc

This file isn't even used in any build.gn files.

Bug: 1105388
Change-Id: I4b4ab6c7c24b1f260b8a4cbb2c3c02697bba7574
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2296086
Commit-Queue: Maksim Moskvitin <mmoskvitin@google.com>
Commit-Queue: Marc Treib <treib@chromium.org>
Auto-Submit: Maksim Moskvitin <mmoskvitin@google.com>
Reviewed-by: Marc Treib <treib@chromium.org>
Cr-Commit-Position: refs/heads/master@{#790761}

components/invalidation/impl/invalidator.cc

-// Copyright 2014 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 "components/invalidation/impl/invalidator.h"
-
-namespace syncer {
-
-Invalidator::Invalidator() {
-}
-
-Invalidator::~Invalidator() {
-}
-
-bool Invalidator::UpdateRegisteredIds(InvalidationHandler* handler,
-                                      const Topics& ids) {
-  NOTREACHED();
-  return false;
-}
-}  // namespace syncer