Fix uses of /deep/ in trace viewer.

tracing/tracing/ui/base/tool_button.css

Index: tracing/tracing/ui/base/tool_button.css
diff --git a/tracing/tracing/ui/base/tool_button.css b/tracing/tracing/ui/base/tool_button.css
deleted file mode 100644
index 1c5ae4170c0781ef346b7b9f10ea3cd935204313..0000000000000000000000000000000000000000
--- a/tracing/tracing/ui/base/tool_button.css
+++ /dev/null
@@ -1,17 +0,0 @@
-/* Copyright (c) 2013 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.
- */
-
-* /deep/ .tool-button {
-  background-position: center center;
-  background-repeat: no-repeat;
-  border-bottom: 1px solid #BCBCBC;
-  border-top: 1px solid #F1F1F1;
-  cursor: pointer;
-  height: 30px;
-}
-
-* /deep/ .tool-button.active {
-  cursor: auto;
-}