fast/dom/error-to-string-stack-overflow.html started failing on Windows 7 Release (Tests) between r91115 and r91116 (inclusive).
I think this just needs new results. The test deliberately triggers a stack overflow, and doesn't catch it, so the error is printed to the console. Previously RangeError had the wrong prototype, and didn't convert the error into a useful error message, printing a blank line in the console. Since r91116 we inherit from Error correctly, and print the error to the console.
Thanks for the analysis, Gavin. Could you update the results by grabbing them from the bot? "webkit-patch rebaseline" might be the easiest way.
Created attachment 101391 [details]
Fixed in r91305