[WIP] BufferedInputRouter

[WIP] BufferedInputRouter

This is meant as a tracking patch for all pending patches/changes that implement
the BufferedInputRouter. This is not meant to be reviewed directly; constituent
patches will be submitted invididually.

The BufferedInputRouter batches input events into EventPackets. The delivery of
these packets is synchronized with BeginFrame; a call to BeginFrame will flush
the pending EventPacket, and the BeginFrame will be forwarded only after the
packet response has been received.

BUG=245499

[jdduke (slow), 2013-08-30 00:46:09]

nduca@, I've tried to follow the spirit of our discussion on augmenting input
types in the browser and renderer for process-specific functionality.  This is a
first pass at that: for the relevant additions, PLEASE simply look at the diff
of the very latest patch upload.   No need to look at the entire patch, as the
various components have already been reviewed seprately.

The new approach lets us decouple ack logic completely from the InputQueue, and
unifies how events are dispatched in the renderer.  Adding additional payload
types (e.g., ui::Event) should be relatively painless in the future. 

If this is not at all the direction you had in mind, let me know; I plan to
flesh out the unit tests tomorrow.

[jdduke (slow), 2013-09-03 18:24:07]

On 2013/08/30 00:46:09, jdduke wrote:
> nduca@, I've tried to follow the spirit of our discussion on augmenting input
> types in the browser and renderer for process-specific functionality.  This is
a
> first pass at that: for the relevant additions, PLEASE simply look at the diff
> of the very latest patch upload.   No need to look at the entire patch, as the
> various components have already been reviewed seprately.
> 
> The new approach lets us decouple ack logic completely from the InputQueue,
and
> unifies how events are dispatched in the renderer.  Adding additional payload
> types (e.g., ui::Event) should be relatively painless in the future. 
> 
> If this is not at all the direction you had in mind, let me know; I plan to
> flesh out the unit tests tomorrow.

Hmmm, I uploaded a rebase so patch set 10 is the patch set you're looking for...

[nduca, 2013-09-03 21:48:43]

this lg to start breaking apart to land. i'd start with input, then input packet
and onward from there