Update DisplayScheduler to handle pushed BeginFrames

We are looking to eliminate Missed BeginFrames. As the arrive in clients
too late to make deadlines. Resulting in various backpressure mechanisms
slowing down frame production.

However `ExternalBeginFrameSourceMojo` is used without a `remote_client`
in AR mode. In this mode the `ArCompositorFrameSink::RequestBeginFrame`
pushes one BeginFrame at a time to Viz. Using GPU fences as backpressure
to prevent future frames.

`ExternalBeginFrameSourceMojo::IssueExternalBeginFrame` is reliant on
the Missed BeginFrames as a side-effect of
`viz::Display::SetNeedsOneBeginFrame` to trigger frame production. As
otherwise the `DisplayScheduler` will subscribe to BeginFrames and wait
for the next one.

To handle this we are adding `BeginFrameArgs` to the
`SetNeedsOneBeginFrame`. So that we can immediately use the args if we
are not already subscribed. In all future VSyncs the `DisplayScheduler`
will already be subscribed and trigger frame production through
normal notifications.

Bug: 40900977
Change-Id: I84c8faedda7b1106c9539cafc528c027de34b427
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6674264
Reviewed-by: Vasiliy Telezhnikov <vasilyt@chromium.org>
Commit-Queue: Jonathan Ross <jonross@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1490804}