Surfaces should acknowledge frame submissions

Surfaces should acknowledge frame submissions

Previously, there was no way for clients of the surfaces service to
appropriately rate-limit their frame submissions. We tried using the "return
resources" signal to rate-limit, but that's really a measure of how quickly
you're submitting new resources rather than how quickly the system is putting
up frames.

Currently, only the Sky compositor listens to this signal. Using this signal,
we're able to run sky/examples/spinning-square.sky in sync with the surfaces
service (that is, submitting exactly one frames every 17ms).

R=jamesr@chromium.org

Committed: https://chromium.googlesource.com/external/mojo/+/3374c8e724eb43c7ec1813999144dcc5f435c219

[jamesr, 2014-11-24 20:42:02]

Now that you have a state machine you probably want to add a unit test or two
that drive through the states to make sure you don't get stuck.  With 3 states
it's pretty clear, but as you get more (and you probably will) it'll be harder
to reason through the transitions unassisted.

lgtm

https://codereview.chromium.org/756673004/diff/1/mojo/services/public/interfa...
File mojo/services/public/interfaces/surfaces/surfaces.mojom (right):

https://codereview.chromium.org/756673004/diff/1/mojo/services/public/interfa...
mojo/services/public/interfaces/surfaces/surfaces.mojom:65:
SubmitFrame(SurfaceId id, Frame frame) => ();
can you document the callback a bit?

[abarth-chromium, 2014-11-25 00:21:57]

Committed patchset #1 (id:1) manually as
3374c8e724eb43c7ec1813999144dcc5f435c219 (presubmit successful).