Remove old tracing code now that it has moved to third_party.

chrome/browser/resources/tracing/tracing_controller.css

-/* 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. */
-
-.tracing-overlay {
-  -webkit-box-align: center;
-  -webkit-box-orient: vertical;
-  -webkit-box-pack: center;
-  display: -webkit-box;
-  height: 80px;
-  text-align: center;
-  width: 200px;
-}
-
-.tracing-start-button {
-  -webkit-margin-start: 5px;
-  background: rgb(255, 0, 0);
-  background-clip: border-box;
-  border: 1px solid black;
-  border-bottom: 0;
-  border-top-left-radius: 8px;
-  border-top-right-radius: 8px;
-  display: inline-block;
-  margin-top: 4px;
-  padding: 5px 10px 3px 10px;
-  position: fixed;
-  right: 3px;
-  text-align: center;
-  text-decoration: none;
-  top: -1px;
-}