Timeline: bring back FirstPaint marker and remove brown ticks near frame markers

Source/devtools/front_end/timeline/timelinePanel.css

 /*
  * Copyright (C) 2006, 2007, 2008 Apple Inc.  All rights reserved.
  * Copyright (C) 2009 Anthony Ricaud <rik@webkit.org>
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 455 matching lines @@
     bottom: auto;
     content: "";
     display: block;
 }
 
 .timeline .resources-event-divider:hover::before {
     width: 4px;
     margin: 0 1px;
 }
 
+.timeline .resources-event-divider.timeline-frame-divider::before {
+    display: none;
+}
+
 .timeline .resources-event-divider.resources-red-divider::before {
     background-color: rgb(255, 0, 0);
 }
 
 .timeline .resources-event-divider.resources-blue-divider::before {
     background-color: rgb(0, 0, 255);
 }
 
 .timeline .resources-event-divider.resources-orange-divider::before {
     background-color: rgb(255, 178, 23);
@@ skipping 447 matching lines @@
 
 .timeline-layers-view-properties td {
     border: 1px solid #e1e1e1;
     line-height: 22px;
 }
 
 .timeline-paint-profiler-log-split .split-view-contents-first {
     background-color: #eee;
     z-index: 0;
 }