`move_traffic_light` was framing the close / minimize / zoom NSButtons
at `titlebar_height - traffic_light_position.y - button_h`. Once the
window opts into `NSFullSizeContentViewWindowMask`, the content layout
rectangle covers the whole frame and `titlebar_height()` returns 0 —
collapsing the origin to a large negative Y. macOS still painted the
buttons through its own caching layer at the title bar's natural
position, but the buttons' hit-test rectangle followed the frame off
screen, so clicking close / minimize / zoom did nothing.
Anchor the math against the close button's actual superview frame
height (the themeFrame, which equals the window height in Y-up
coordinates) so the visual position and the hit area stay in lockstep
no matter what mask combination the window opens with. `titlebar_height`
stays available for callers that want the legacy non-full-size
interpretation, with `#[allow(dead_code)]` and a docstring pointing at
this fix.
Root cause of the post-tab lag: the GPUI 16 ms timer was calling
`WebSurfaceRuntime::ensure_tab` and `tick` on the UI thread, and each
call did a synchronous `serde_json` write plus `read_line` against the
Servo sidecar over stdin/stdout. With even one visible tab, every
frame stalled on cross-process IPC.
Introduce `web_surface_worker.rs` — a per-profile worker thread that
owns the `ServoLiveClient`, drains a coalescing request queue
(latest Ensure/Poll per tab wins, no unbounded growth), and ships
results back through a `std::sync::mpsc` channel. `WebSurfaceRuntime`
now submits work non-blockingly and drains responses in `tick`; the
UI thread never blocks on the sidecar.
Adjacent in-flight cleanup riding along: hardware IOSurface
rendering-context completion (sidecar `live_protocol`,
`hardware_rendering_context`, GPUI BGRA surface shader), CSS viewport
size + device pixel ratio plumbing into `ServoLiveFrame`, and the
Send opt-ins for `CVPixelBuffer`-bearing types so frames can cross
the thread boundary.
ZacharyZhang-NY