Mentioned that the fix in bug 56909 may have caused crashes: http://build.chromium.org/p/chromium.webkit/builders/Win%20Reliability/builds/1200/steps/reliability%3A%20partial%20result%20of%20current%20build/logs/stdio
Oops, I filed another bug (bug 57221). See that bug for detailed crash signature. *** This bug has been marked as a duplicate of bug 57221 ***