Description of Change

Resolves #50432.

This is a pure Chromium patch and should probably be upstreamed. This fix was also came to through many conversations with AI.

Context

Pressing Backspace inside a contenteditable element incorrectly accepts macOS text replacements. This patch adds a check right before Chromium commits to accepting a text replacement with the following logic:

“If this replacement callback was created for an older snapshot of the text, only allow it to proceed if the current caret has moved past the replacement range. Otherwise, treat it as stale and ignore it.”

This is enough to bail early on Backspace, so it patches the bug. The check is (hopefully) sensible logic, but it does not address any underlying issues as to what causes a Backspace press to go down that text replacement acceptance path. That is a larger architectural issue which this patch does not attempt to address.

The bug does not exhibit in Safari (arguably because it follows the Input Events Level 2 spec more closely than Chromium; specifically around the use of the insertReplacementText value for the inputType property on events, but also event ordering). There is an issue around the inputType spec deviation filed for Chromium, but it started in 2019, and there has not been much movement since. Regardless, due to the behavior discrepancy, even with this patch there are remaining bugs in downstream libraries that use contenteditable (like Lexical, which many Electron apps use), but those can be addressed separately.

Longer-term, all bugs in this area may be more-properly addressed with an architectural alignment of Chromium with Safari when it comes to macOS text replacements in contenteditable elements.

Checklist

• I have built and tested this change
• I have filled out the PR description
• I have reviewed and verified the changes
• npm test passes
• PR release notes describe the change in a way relevant to app developers, and are capitalized, punctuated, and past tense.

Release Notes

Notes: Fixed buggy behavior where Backspace would accept macOS text replacements inside contenteditable elements.