[Testing] anyrender_skia Graphite backend (anyrender#103) + skia_paint_bench

[nicoburns]

Summary

A testing PR for DioxusLabs/anyrender#103, which adds an opt-in Skia Graphite backend on macOS/iOS. Don't merge as is: it patches all anyrender crates to that PR's git branch.

Opting into Graphite

• The workspace anyrender_skia dependency now sets default-features = false. Each feature picks an engine explicitly, because rust-skia only publishes prebuilt binaries with a single GPU engine.
  • skia / skia-pixels / skia-softbuffer enable anyrender_skia/ganesh, the same engine as before.
  • The new skia-graphite feature enables anyrender_skia/graphite. It exists in dioxus-native, browser and readme, and is only different from skia on Apple.
• Example: cargo run --release -p rdme --no-default-features --features skia-graphite,comrak,floats -- https://github.com/DioxusLabs/blitz

New examples/skia_paint_bench (macOS only)

• Renders a page offscreen on Metal. It's modelled on paint_bench, which doesn't support Skia.
• Each frame is timed in two parts:
  • paint_scene: blitz_paint::paint_scene → SkiaScenePainter.
  • rasterize: Ganesh flush_submit_and_sync_cpu, or Graphite snap + insert_recording + submit_and_wait.
• It's a separate crate because only one engine can be enabled per build if you want prebuilt binaries:

cargo run --release -p skia_paint_bench -- <url> [width] [height] [scale] [iters]                                       # Ganesh
cargo run --release -p skia_paint_bench --no-default-features --features graphite -- <url> [width] [height] [scale] [iters]  # Graphite

Results

• Measured on the Devin macOS VM (VirtualMac2,1: paravirtualized GPU, 8 vCPUs, with a background iOS simulator adding load). Absolute numbers aren't representative of real Apple hardware.
• 1366x768@2x. Each figure is the median of 5 runs; each run's value is the median of 300 frames. Times in µs:

page	engine	paint_scene	rasterize	total
servo.org	Ganesh	65	632	695
	Graphite	104	749	850
news.ycombinator.com	Ganesh	288	760	1054
	Graphite	432	653	1095
en.wikipedia.org/wiki/Rust_(programming_language)	Ganesh	276	1871	2150
	Graphite	413	2006	2427
github.com/DioxusLabs/blitz	Ganesh	594	2544	3156
	Graphite	608	2435	3058

• Graphite spends about 1.5x longer recording draw calls (paint_scene) on 3 of the 4 pages. Rasterize time is within ±15%, faster on some pages and slower on others. Totals range from 3% faster to 22% slower.
• No Skia warnings were logged with Graphite on any of these pages.

rdme on Graphite:

Link to Devin session: https://dioxus.staging.devinenterprise.com/sessions/7b8d8492640e46d08ea6cd8b5ab63dbb
Open in Devin Desktop: https://dioxus.staging.devinenterprise.com/desktop/session/7b8d8492640e46d08ea6cd8b5ab63dbb?variant=devin-insiders
Requested by: @nicoburns

WPT results

No changes in test results compared to main.

_{Generated by the WPT workflow.}

[staging-devin-ai-integration]

I'll fix CI failures and address comments from users with write access that start with 'Devin'.

• Disable automatic comment, CI, and merge conflict monitoring