DevTools: Allow timeline details scrolling with keyboard.

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

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  * Copyright (C) 2012 Intel 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 1265 matching lines @@
    */
   constructor(timelineModel, filters, delegate) {
     super();
     this.element.classList.add('timeline-details');
 
     var tabIds = Timeline.TimelinePanel.DetailsTab;
     this._defaultDetailsWidget = new UI.VBox();
     this._defaultDetailsWidget.element.classList.add('timeline-details-view');
     this._defaultDetailsContentElement =
         this._defaultDetailsWidget.element.createChild('div', 'timeline-details-view-body vbox');
+    this._defaultDetailsContentElement.tabIndex = 0;
     this.appendTab(tabIds.Details, Common.UIString('Summary'), this._defaultDetailsWidget);
     this.setPreferredTab(tabIds.Details);
 
     /** @type Map<string, Timeline.TimelineTreeView> */
     this._rangeDetailViews = new Map();
 
     var bottomUpView = new Timeline.BottomUpTimelineTreeView(timelineModel, filters);
     this.appendTab(tabIds.BottomUp, Common.UIString('Bottom-Up'), bottomUpView);
     this._rangeDetailViews.set(tabIds.BottomUp, bottomUpView);
 
@@ skipping 623 matching lines @@
   }
 
   /**
    * @override
    * @param {!SDK.Target} target
    */
   targetRemoved(target) {
     this._targets.remove(target, true);
   }
 };