In bug 1625590 we're seeing very high heap unclassified due to fonts sort of leaking. We understand what's going but we're going to be conservative and disable WebRender for this release.

Tracking for 82 rc2.

We believe that the memory growth affects Release users more than Nightly users because Nightly users restart their browser more often (to update) and have less of a chance to accumulate a lot of font memory over time.

Beta 82 was the first Beta to have WebRender enabled in late Beta; having one more cycle before rollout seems like the right thing to do.

This patch should only land in 82 beta. 83 will be the new rollout target for MacOS.

Comment on attachment 9181324 [details]
Bug 1670961 - Disable WebRender in OSX release builds.

Beta/Release Uplift Approval Request

• User impact if declined: They will get WR and possibly suffer the effects described in bug 1625590.
• Is this code covered by automated tests?: Yes
• Has the fix been verified in Nightly?: No
• Needs manual test from QE?: Yes
• If yes, steps to reproduce: Run Firefox on Mac OS X, any version. Check about:support, it should use OpenGL compositing, not WebRender.
• List of other uplifts needed: None
• Risk to taking this patch: Low
• Why is the change risky/not risky? (and alternatives if risky): We are deferring shipping WebRender for one more release. The OpenGL backend has shipped many times without issue.
• String changes made/needed:

Comment on attachment 9181324 [details]
Bug 1670961 - Disable WebRender in OSX release builds.

approved for 82 rc2

https://hg.mozilla.org/releases/mozilla-release/rev/bbdea0acf29a60ac9500439691337f3e0e96eb2f

Verified as fixed in the latest Firefox 82 RC on Mac OS X 10.15 - OpenGL compositing is displayed in about:support.