browser: fix flaky TestPageScreenshotFullpage - #5985
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Wait for the browser to commit a frame after injecting the gradient div so the screenshot captures the painted gradient instead of racing the first paint and getting a white background on slow CI runners.
mstoykov
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What?
After injecting the gradient
<div>inTestPageScreenshotFullpage, wait for tworequestAnimationFrames before taking the full-page screenshot, so Chromium is guaranteed to have laid out and painted the new content.Why?
The test intermittently fails on CI with the bottom pixel coming back white (e.g.
R: 65535, B: 65535) instead of the expected dominant blue. TheEvaluatecall resolves as soon as the JS returns, but the appended gradient node is not guaranteed to have been painted before the subsequentPage.captureScreenshotCDP call. On a slow/contended runner the screenshot can race the first paint and capture the still-white background. Awaiting two rAFs ensures a frame has been committed before the screenshot is requested.Checklist
make check) and all pass.Related PR(s)/Issue(s)
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