This removes a lot of the plumbing for having the platform embed itself
through IPC which was required for B2G running the browser as both
shell and browser application.
Based on FranklinDM's follow-up for the issue.
This would require browser FE changes, particularly removing the associated
code in `tabbrowser.xml`, however, that was already done in Pale Moon previously.
Other front-end applications may need to take note, though.
Based on changes from the following bugs:
* Bug 696398 - Need an api to analyze panning performance
* Bug 800031 - Include paint time in tab switch telemetry
* Bug 820167 - Enable performance measurement of tab animation
* Bug 826383 - Improve Start/Stop FrameTimeRecording for telemetry usage
* Rename nsIDOMEventTarget::PreHandleEvent to nsIDOMEventTarget::GetEventTargetParent
* Add nsIDOMEventTarget::PreHandleEvent
* Add EventTargetChainItem::GetFirstEventTarget
* Call EventTargetChainItem::PreHandleEvent even it sets mCanHandle=false
* Move form control frame focus/blur from nsGenericHTMLFormElement::GetEventTargetParent to PreHandleEvent
* Move fire change event from HTMLTextAreaElement::GetEventTargetParent to PreHandleEvent
* Refine nsXULElement::GetEventTargetParent
* Move dispatch XUL command from nsXULElement::GetEventTargetParent to PreHandleEvent
* Move fire events and set value from HTMLInputElement::GetEventTargetParent to PreHandleEvent
* Add test case
* Let HTMLInputElement delegate event handling to it's parent class
* Refine EventTargetChain flags to reduce overheads
* Refine event target chain creation
* Refine assertion in EventTargetChainItem::Create
Tag #1375