Remove remains of webrtc/base

webrtc/base/thread_checker_impl.h

Index: webrtc/base/thread_checker_impl.h
diff --git a/webrtc/base/thread_checker_impl.h b/webrtc/base/thread_checker_impl.h
deleted file mode 100644
index 3a0a6c73152cc492808eae16cfb57d01a3e0a794..0000000000000000000000000000000000000000
--- a/webrtc/base/thread_checker_impl.h
+++ /dev/null
@@ -1,21 +0,0 @@
-/*
- *  Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
- *
- *  Use of this source code is governed by a BSD-style license
- *  that can be found in the LICENSE file in the root of the source
- *  tree. An additional intellectual property rights grant can be found
- *  in the file PATENTS.  All contributing project authors may
- *  be found in the AUTHORS file in the root of the source tree.
- */
-
-// Borrowed from Chromium's src/base/threading/thread_checker_impl.h.
-
-#ifndef WEBRTC_BASE_THREAD_CHECKER_IMPL_H_
-#define WEBRTC_BASE_THREAD_CHECKER_IMPL_H_
-
-
-// This header is deprecated and is just left here temporarily during
-// refactoring. See https://bugs.webrtc.org/7634 for more details.
-#include "webrtc/rtc_base/thread_checker_impl.h"
-
-#endif  // WEBRTC_BASE_THREAD_CHECKER_IMPL_H_