No, it fails on nightly because of some platform exception happening when you try to stringify document.location.__proto__. I'll reset this change and do it instead in bug 846290.

You can reproduce it in webconsole:`String(document.location.__proto__)`
`[Exception... "Illegal operation on WrappedNative prototype object"  nsresult: "0x8057000c (NS_ERROR_XPC_BAD_OP_ON_WN_PROTO)"  location: "JS frame :: resource://gre/modules/devtools/WebConsoleUtils.jsm :: WCU_formatResult :: line 251"  data: no]`