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

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

Index: third_party/WebKit/Source/devtools/front_end/ui/splitWidget.css
diff --git a/third_party/WebKit/Source/devtools/front_end/ui/splitWidget.css b/third_party/WebKit/Source/devtools/front_end/ui/splitWidget.css
index e95ae68374a73b356f59a95181995b955537f376..9c93d7e8e90f8a8f43bb8ac4ac63d285cfa389c4 100644
--- a/third_party/WebKit/Source/devtools/front_end/ui/splitWidget.css
+++ b/third_party/WebKit/Source/devtools/front_end/ui/splitWidget.css
@@ -78,6 +78,10 @@
     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%);