More about:gpu tracing improvements.

chrome/browser/resources/gpu_internals/timeline.css

 /*
 Copyright (c) 2011 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.
 */
 .timeline {
   -webkit-user-select: none;
 }
 
-.timeline-track {
+.timeline-drag-box {
+  position: fixed;
+  background-color: rgba(0, 0, 255, 0.25);
+  border: 1px solid rgb(0, 0, 96);
+}
+
+.timeline-thread-track {
+  display: -webkit-box;
+  -webkit-box-orient: vertical;
+  padding-top: 1px;
+  padding-bottom: 1px;
+}
+
+.timeline-thread-track:not(:first-child) {
+  border-top: 1px solid #D0D0D0;
+}
+
+.timeline-slice-track {
   display: -webkit-box;
   -webkit-box-orient: horizontal;
   -webkit-box-align: stretch;
   background-color: white;
   padding-right: 5px;
   margin: 0;
   padding: 0;
   height: 18px;
 }
 
-.timeline-drag-box {
-  position: fixed;
-  background-color: rgba(0, 0, 255, 0.25);
-  border: 1px solid rgb(0, 0, 96);
-}
-
-.timeline-track:not(:first-child) {
-  border-top: 1px solid #D0D0D0
-}
-
-.timeline-track-title {
+.timeline-slice-track-title {
   text-align: right;
   overflow: visible;
   width: 150px;
   padding-right: 5px;
 }
 
-.timeline-track-canvas-container {
+.timeline-slice-track-canvas-container {
   -webkit-box-flex: 1;
   width: 100%;
 }
 
-.timeline-track-canvas {
+.timeline-slice-track-canvas {
   -webkit-box-flex: 1;
   width: 100%;
   height: 100%;
 }