Similarly:
  CanvasResourceDispatcher::PrepareFrame is generating new ids in response to resize at frame submission time.
  VideoFrameSubmitter::SubmitFrame is generating new ids in response to resize at frame submittion time.

I noticed that requests to change offscreen canvas's size come from javascript. It's not possible to pass a LocalSurfaceId alongside the size, so it has to be the child that allocates the id. It's still possible to get rid of OnFirstSurfaceActivation. I'm going to establish a mojo connection between the submitter and SurfaceLayerBridge mediated by the browser, so that every time a new id is allocated we can notify SurfaceLayerBridge without necessarily waiting for activation.

Why is it not possible to pass a LocalSurfaceId alongside the size?

Because I don't know how to do that over javascript.

Perhaps jbroman@ can help here provide some guidance? Jeremy?

If we align the allocation with size change (as opposed to BeginFrame) we won't have to worry about one frame latency and I don't think it would be a big deal if the child does the allocation.

I don't really understand surfaces well enough to have an informed opinion here. Author script presumably has no idea what a "local surface ID" is as that's a Chromium implementation detail, but I don't know how that relates to surface allocation.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/d2f538cffc7ef006234a6beae7e2411ca49d4c30

commit d2f538cffc7ef006234a6beae7e2411ca49d4c30
Author: Saman Sami <samans@chromium.org>
Date: Mon Nov 19 22:24:59 2018

Stop sending OnFirstSurfaceActivation to SurfaceLayerBridge

Establish a direct connection from the child (CanvasResourceDispatcher/
VideoFrameSubmitter) to the embedder (SuraceLayerBridge) so the child
can notify the embedder of its allocated SurfaceIds directly instead of
three process hops (renderer->viz->browser->renderer), hence reducing
latency and eliminating any IPC messages involved in this process.

Bug: 893850,883927
Change-Id: Ide595e3c6aa995c77678d6413d5ad6421e2d35e5
Reviewed-on: https://chromium-review.googlesource.com/c/1338411
Commit-Queue: Saman Sami <samans@chromium.org>
Reviewed-by: Robert Flack <flackr@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Reviewed-by: Fady Samuel <fsamuel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609469}
[modify] https://crrev.com/d2f538cffc7ef006234a6beae7e2411ca49d4c30/content/browser/renderer_host/embedded_frame_sink_impl.cc
[modify] https://crrev.com/d2f538cffc7ef006234a6beae7e2411ca49d4c30/content/browser/renderer_host/embedded_frame_sink_impl.h
[modify] https://crrev.com/d2f538cffc7ef006234a6beae7e2411ca49d4c30/content/browser/renderer_host/embedded_frame_sink_provider_impl.cc
[modify] https://crrev.com/d2f538cffc7ef006234a6beae7e2411ca49d4c30/content/browser/renderer_host/embedded_frame_sink_provider_impl.h
[modify] https://crrev.com/d2f538cffc7ef006234a6beae7e2411ca49d4c30/content/browser/renderer_host/embedded_frame_sink_provider_impl_unittest.cc
[modify] https://crrev.com/d2f538cffc7ef006234a6beae7e2411ca49d4c30/third_party/blink/public/platform/modules/frame_sinks/embedded_frame_sink.mojom
[modify] https://crrev.com/d2f538cffc7ef006234a6beae7e2411ca49d4c30/third_party/blink/renderer/platform/graphics/begin_frame_provider.h
[modify] https://crrev.com/d2f538cffc7ef006234a6beae7e2411ca49d4c30/third_party/blink/renderer/platform/graphics/canvas_resource_dispatcher.cc
[modify] https://crrev.com/d2f538cffc7ef006234a6beae7e2411ca49d4c30/third_party/blink/renderer/platform/graphics/canvas_resource_dispatcher.h
[modify] https://crrev.com/d2f538cffc7ef006234a6beae7e2411ca49d4c30/third_party/blink/renderer/platform/graphics/surface_layer_bridge.cc
[modify] https://crrev.com/d2f538cffc7ef006234a6beae7e2411ca49d4c30/third_party/blink/renderer/platform/graphics/surface_layer_bridge.h
[modify] https://crrev.com/d2f538cffc7ef006234a6beae7e2411ca49d4c30/third_party/blink/renderer/platform/graphics/test/mock_embedded_frame_sink_provider.h
[modify] https://crrev.com/d2f538cffc7ef006234a6beae7e2411ca49d4c30/third_party/blink/renderer/platform/graphics/video_frame_submitter.cc
[modify] https://crrev.com/d2f538cffc7ef006234a6beae7e2411ca49d4c30/third_party/blink/renderer/platform/graphics/video_frame_submitter.h
[modify] https://crrev.com/d2f538cffc7ef006234a6beae7e2411ca49d4c30/third_party/blink/renderer/platform/graphics/video_frame_submitter_test.cc