The headerdoc for JSObjectSetPrivateProperty claims that passing NULL as the value is valid. In practice this leads to assertion failures with debug builds of JavaScriptCore.
Created attachment 67113 [details] Patch
Comment on attachment 67113 [details] Patch r=me
http://trac.webkit.org/changeset/67129 might have broken Chromium Mac Release The following changes are on the blame list: http://trac.webkit.org/changeset/67128 http://trac.webkit.org/changeset/67129 http://trac.webkit.org/changeset/67126 http://trac.webkit.org/changeset/67127
Attachment 67113 [details] was posted by a committer and has review+, assigning to Mark Rowe for commit.
This was landed way back in r67129.