Apr 13, 2021, 2:54:52 PMApr 13
to Chromium Embedders, arv...@microsoft.com, Alexei Svitkine, Brian Clifton, bla...@chromium.org, eri...@microsoft.com, fe...@chromium.org, rby...@chromium.org
Checking in on this thread a year later, I wanted to note a few recent cases where Edge behavior has unexpectedly diverged from upstream in part due to Finch flags:
1) FTP Deprecation: Edge disabled FTP by default in the code and Chrome disabled it via Finch. Chrome's Finch config expired, accidentally
re-enabling FTP for Chrome.
2) Cache Partitioning by Network Isolation Key: Chromium has SplitHostCacheByNetworkIsolationKey
set to DISABLED_BY_DEFAULT. However, Chromium calls a function in startup ( SplitCacheFeatureEnableByDefault() ) to enable it by default if there's no finch override. Chrome's Finch is configured to disable this feature at 100% for 89 Stable; Edge did not copy this config. As a result, Edge unknowingly shipped the new split cache back in v88 Stable. Fortunately, nobody seems to have noticed and we got our first complaint/query about this yesterday.
3) ServiceWorker Installation: Finch enables ThrottleInstallingServiceWorker for Chrome 87 and above. Microsoft Teams noticed
that their ServiceWorker installation failed in Edge but not Chrome; after investigation, we found that the absence of this flag caused network errors with Flow Control during the installations' fetch processes.
On an unrelated note: Finch configuration remains perhaps the most impactful non-transparent part of the Chromium project. This leads to even highly sophisticated browser folks getting confused (e.g. thinking H3 is disabled by default
) about how Chromium behaves. Is there any chance that this might be made more transparent in the future?