DevTools: Disable timeline network pane resizer when network group is collapsed.

third_party/WebKit/Source/devtools/front_end/ui/splitWidget.css

 /*
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * 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 60 matching lines @@
 }
 
 .shadow-split-widget.vbox.shadow-split-widget-first-is-sidebar {
     flex-direction: column-reverse !important;
 }
 
 .shadow-split-widget-resizer-border {
     pointer-events: none;
 }
 
+.shadow-split-widget.vbox > .shadow-split-widget-sidebar.no-default-splitter {
+    border: 0 !important;
+}
+
 .shadow-split-widget.vbox > .shadow-split-widget-sidebar:not(.maximized) {
     border: 0;
     border-top: 1px solid rgb(64%, 64%, 64%);
 }
 
 .shadow-split-widget.vbox.shadow-split-widget-first-is-sidebar > .shadow-split-widget-sidebar:not(.maximized) {
     border: 0;
     border-bottom: 1px solid rgb(64%, 64%, 64%);
 }
 
 .shadow-split-widget.hbox > .shadow-split-widget-sidebar:not(.maximized) {
     border: 0;
     border-left: 1px solid rgb(64%, 64%, 64%);
 }
 
 .shadow-split-widget.hbox.shadow-split-widget-first-is-sidebar > .shadow-split-widget-sidebar:not(.maximized) {
     border: 0;
     border-right: 1px solid rgb(64%, 64%, 64%);
 }