#20431 Fix flaky New Tab style switch web test

webviews/test/new-tab-style-switch.test.tsx:68 ("offers its five styles as radios", fieldAsked 1 vs 0) failed about 1 run in 3 on feat-cmux-next and turned PR web gates red. It came in with #20336.

The race was in the test. After a click, the style switch asks for the location field on the next animation frame. The test checks that nothing was asked yet once the click's act() returns. JSDOM's requestAnimationFrame is a real 16 ms timer, so when that act() took longer than a frame on a loaded runner, the frame had already fired and the count was 1.

The test now queues frames and runs them itself. It checks 0 after the click and 1 after one frame, and nothing depends on timing. No retries were added, and the component is unchanged.

Local runs of the focused file (bun test test/new-tab-style-switch.test.tsx):

• base: 2 of 30 failed with Expected: 0, Received: 1
• this branch: 0 of 40 failed

bun run check passes.

The Swift NewTabStyleSwitchTests red is owned separately and not touched here.

Changelog

none

🤖 Generated with Claude Code

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Summary by cubic

Fixes the flaky New Tab style switch web test so PR web gates stop failing intermittently.

• The test now queues requestAnimationFrame callbacks and runs them only when the test asks, instead of relying on JSDOM's 16 ms frame timer.
• The test still checks that no field is asked after the click and one more after one frame, but no longer depends on timing.