[DevTools] Prevent scrollbar flickering while recording allocation timeline.

third_party/WebKit/Source/devtools/front_end/profiler/profilesSidebarTree.css

 /*
  * Copyright 2016 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.
  */
 
 /* Tree outline overrides */
 
 :host {
     padding: 0;
@@ skipping 29 matching lines @@
     margin-top: 1px;
     color: rgb(92, 110, 129);
     text-shadow: rgba(255, 255, 255, 0.75) 0 1px 0;
     line-height: 18px;
 }
 
 .tree-outline li.profiles-tree-section::before {
     display: none;
 }
 
+.tree-outline ol {
+    overflow: hidden;
+}
+
 /* Generic items styling */
 
 .title-container > .save-link {
     text-decoration: underline;
     margin-left: auto;
     display: none;
 }
 
 li.selected .title-container > .save-link {
     display: block;
@@ skipping 116 matching lines @@
     content: url(Images/profileIcon.png);
 }
 
 .profile-sidebar-tree-item.small .icon {
     content: url(Images/profileSmallIcon.png);
 }
 
 .profile-group-sidebar-tree-item .icon {
     content: url(Images/profileGroupIcon.png);
 }