Change how the load and content ready event timestamps are tracked.

https://bugs.webkit.org/show_bug.cgi?id=123356

Reviewed by Joseph Pecoraro.

* UserInterface/DashboardManager.js:
(WebInspector.DashboardManager.prototype._updateTime): Use the timestamps on the main frame.
* UserInterface/Frame.js:
(WebInspector.Frame):
(WebInspector.Frame.prototype.get domContentReadyEventTimestamp): Added.
(WebInspector.Frame.prototype.get loadEventTimestamp): Added.
(WebInspector.Frame.prototype.markDOMContentReadyEvent): Added.
(WebInspector.Frame.prototype.markLoadEvent): Added.
* UserInterface/TimelineManager.js:
(WebInspector.TimelineManager.prototype.eventRecorded.processRecord): Use markLoadEvent and markDOMContentReadyEvent.
Do it for all frames, not just the main frame.
(WebInspector.TimelineManager.prototype.pageDidLoad): Call markLoadEvent on the Frame.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@162398 268f45cc-cd09-0410-ab3c-d52691b4dbfc