DevTools: do not update timeline tree view details if not visible.

third_party/WebKit/Source/devtools/front_end/timeline/TimelineTreeView.js

Index: third_party/WebKit/Source/devtools/front_end/timeline/TimelineTreeView.js
diff --git a/third_party/WebKit/Source/devtools/front_end/timeline/TimelineTreeView.js b/third_party/WebKit/Source/devtools/front_end/timeline/TimelineTreeView.js
index 75c98695af596f75a623d706490c995b2f7eab2b..3ad13c710376d337a84f84008919e8ad4b230668 100644
--- a/third_party/WebKit/Source/devtools/front_end/timeline/TimelineTreeView.js
+++ b/third_party/WebKit/Source/devtools/front_end/timeline/TimelineTreeView.js
@@ -84,6 +84,7 @@ Timeline.TimelineTreeView = class extends UI.VBox {
     this._splitWidget.setSidebarWidget(this._detailsView);
     this._splitWidget.hideSidebar();
     this._splitWidget.show(this.element);
+    this._splitWidget.addEventListener(UI.SplitWidget.Events.ShowModeChanged, this._updateDetailsForSelection, this);
 
     /** @type {?TimelineModel.TimelineProfileTree.Node|undefined} */
     this._lastSelectedNode;
@@ -358,6 +359,8 @@ Timeline.TimelineTreeView = class extends UI.VBox {
     if (selectedNode === this._lastSelectedNode)
       return;
     this._lastSelectedNode = selectedNode;
+    if (this._splitWidget.showMode() === UI.SplitWidget.ShowMode.OnlyMain)
+      return;
     this._detailsView.detachChildWidgets();
     this._detailsView.element.removeChildren();
     if (!selectedNode || !this._showDetailsForNode(selectedNode)) {