DevTools: migrate sidebar pane's titleElement to use Toolbar.

Source/devtools/front_end/profiler/profilesPanel.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 96 matching lines @@
     text-decoration: underline;
     margin-left: auto;
     display: none;
 }
 
 .sidebar-tree-item.selected .title-container > .save-link {
     display: block;
 }
 
 .cpu-profile-view {
-    display: none;
+    display: flex;
     overflow: hidden;
 }
 
-.cpu-profile-view.visible {
-    display: flex;
-}
-
 .cpu-profile-view .data-grid {
     border: none;
     flex: auto;
 }
 
 .cpu-profile-view .data-grid th.self-column,
 .cpu-profile-view .data-grid th.total-column {
     text-align: center;
 }
 
@@ skipping 123 matching lines @@
     bottom: 0;
 }
 
 #cpu-profile-flame-chart-overview-grid .resources-dividers-label-bar {
     pointer-events: auto;
 }
 
 .cpu-profile-flame-chart-overview-pane {
     flex: 0 0 80px !important;
 }