Findit identified the culprit r565676 with confidence 70.0% in the config "chromium.memory / Linux MSan Tests"
based on the flakiness trend:

https://findit-for-me.appspot.com/waterfall/flake?key=ag9zfmZpbmRpdC1mb3ItbWVygAILEhdNYXN0ZXJGbGFrZUFuYWx5c2lzUm9vdCLJAWNocm9taXVtLm1lbW9yeS9MaW51eCBNU2FuIFRlc3RzLzEwMzA5L2Jyb3dzZXJfdGVzdHMvUW1GamEyZHliM1Z1WkVabGRHTm9Rbkp2ZDNObGNsUmxjM1F1VDJabWJHbHVaVWwwWlcxRGIyeHNaV04wYVc5dVgxWmxjbWxtZVZKbGMyOTFjbU5sUkc5M2JteHZZV1JsWkZkb1pXNUViM2R1Ykc5aFpGUnZkR0ZzVEdGeVoyVnlWR2hoYmtGamRIVmhiRk5wZW1VPQwLEhNNYXN0ZXJGbGFrZUFuYWx5c2lzGAEM


Automatically posted by the findit-for-me app (https://goo.gl/Ot9f7N).
Feedback is welcome! Please use component Tools>Test>FindIt>Flakiness

rayankans@, could you take a look?

Ack, looking into this

Detected 3 new flakes for test/step "BackgroundFetchBrowserTest.OfflineItemCollection_VerifyResourceDownloadedWhenDownloadTotalLargerThanActualSize". To see the actual flakes, please visit https://chromium-try-flakes.appspot.com/all_flake_occurrences?key=ahVzfmNocm9taXVtLXRyeS1mbGFrZXNyeQsSBUZsYWtlIm5CYWNrZ3JvdW5kRmV0Y2hCcm93c2VyVGVzdC5PZmZsaW5lSXRlbUNvbGxlY3Rpb25fVmVyaWZ5UmVzb3VyY2VEb3dubG9hZGVkV2hlbkRvd25sb2FkVG90YWxMYXJnZXJUaGFuQWN0dWFsU2l6ZQw. This message was posted automatically by the chromium-try-flakes app. Since flakiness is ongoing, the issue was moved back into Sheriff Bug Queue (unless already there).

I already have a path underway to disable the test: https://chromium-review.googlesource.com/c/chromium/src/+/1095183

(discovered in crbug/851229 which is likely related).