The startTime and endTime were not correct when Network timeline needed to be taken into
account (due to its dynamic loading nature.) This creates a network Timeline for the purposes
of tracking the ResourceTimelineRecords and getting accurate start and end times.

Also changes the way TimelineRecord tracks the inactive portion of time, needed for later
work on the timeline graphs.

https://bugs.webkit.org/show_bug.cgi?id=126676

Reviewed by Joseph Pecoraro.

* UserInterface/ResourceTimelineRecord.js:
(WebInspector.ResourceTimelineRecord.prototype.get updatesDynamically):
(WebInspector.ResourceTimelineRecord.prototype.get usesActiveStartTime):
(WebInspector.ResourceTimelineRecord.prototype.get startTime):
(WebInspector.ResourceTimelineRecord.prototype.get activeStartTime):
(WebInspector.ResourceTimelineRecord.prototype.get endTime):
* UserInterface/Timeline.js:
(WebInspector.Timeline):
(WebInspector.Timeline.prototype.get startTime):
(WebInspector.Timeline.prototype.get endTime):
(WebInspector.Timeline.prototype.addRecord):
(WebInspector.Timeline.prototype._updateTimesIfNeeded):
(WebInspector.Timeline.prototype._recordUpdated):
* UserInterface/TimelineRecord.js:
(WebInspector.TimelineRecord.prototype.get startTime):
(WebInspector.TimelineRecord.prototype.get activeStartTime):
(WebInspector.TimelineRecord.prototype.get endTime):
(WebInspector.TimelineRecord.prototype.get inactiveDuration):
(WebInspector.TimelineRecord.prototype.get activeDuration):
(WebInspector.TimelineRecord.prototype.get updatesDynamically):
(WebInspector.TimelineRecord.prototype.get usesActiveStartTime):
* UserInterface/TimelineRecording.js:
(WebInspector.TimelineRecording.prototype._timelineTimesUpdated):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@162402 268f45cc-cd09-0410-ab3c-d52691b4dbfc