DevTools: brush up paint marker rendering, sort experiments, restore event markers on the overview.

third_party/WebKit/Source/devtools/front_end/perf_ui/timelineGrid.css

 /*
  * Copyright (c) 2015 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.
  */
 
 .resources-dividers {
     position: absolute;
     left: 0;
     right: 0;
@@ skipping 28 matching lines @@
 .resources-divider {
     position: absolute;
     width: 1px;
     top: 0;
     bottom: 0;
     background-color: rgba(0, 0, 0, 0.1);
 }
 
 .resources-event-divider {
     position: absolute;
-    width: 2px;
+    width: 1px;
     top: 0;
     bottom: 0;
     z-index: 300;
 }
 
 .resources-divider-label {
     position: absolute;
     top: 4px;
     right: 3px;
     font-size: 80%;
     white-space: nowrap;
     pointer-events: none;
 }
 
 .timeline-grid-header {
     height: 20px;
     pointer-events: none;
 }