Clean up Timelines code by using ES6 features and less global access of TimelineRecording.

Also don't recreate Timeline objects when TimelineRecording is reset, reset them instead.

https://bugs.webkit.org/show_bug.cgi?id=127157

Reviewed by Joseph Pecoraro.

* UserInterface/LayoutTimelineView.js:
(WebInspector.LayoutTimelineView.prototype.reset):
* UserInterface/NetworkTimeline.js:
(WebInspector.NetworkTimeline):
(WebInspector.NetworkTimeline.prototype.reset):
* UserInterface/NetworkTimelineView.js:
(WebInspector.NetworkTimelineView.prototype.reset):
* UserInterface/OverviewTimelineView.js:
(WebInspector.OverviewTimelineView.prototype._networkTimelineRecordAdded):
* UserInterface/ScriptTimelineView.js:
(WebInspector.ScriptTimelineView.prototype.reset):
* UserInterface/Timeline.js:
(WebInspector.Timeline):
(WebInspector.Timeline.prototype.reset):
* UserInterface/TimelineContentView.js:
(WebInspector.TimelineContentView.set createPathComponent):
(WebInspector.TimelineContentView.set var):
(WebInspector.TimelineContentView.prototype.showOverviewTimelineView):
(WebInspector.TimelineContentView.prototype.showTimelineView):
(WebInspector.TimelineContentView.prototype._showTimelineView):
(WebInspector.TimelineContentView.prototype._update):
(WebInspector.TimelineContentView.prototype._recordingReset):
* UserInterface/TimelineRecording.js:
(WebInspector.TimelineRecording.prototype.reset):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@162418 268f45cc-cd09-0410-ab3c-d52691b4dbfc