Because getting a JSContext can maybe gc, or so the rooting analysis thinks, so we can't root inside them. The good news is that passing in a handle is easy.

We could also try to change nsIXPCScriptable to take handles here, but I'd rather work on removing them all instead

Comment on attachment 752366 [details] [diff] [review] Make some nsIXPConnectWrappedNative methods take a Handle<jsid> instead of a jsid. Review of attachment 752366 [details] [diff] [review]: ----------------------------------------------------------------- ::: js/xpconnect/src/XPCWrappedNative.cpp @@ +2998,5 @@ > return NS_OK; > } > > +/* XPCNativeInterface FindInterfaceWithMember (in JSHandleId name); */ > +NS_IMETHODIMP XPCWrappedNative::FindInterfaceWithMember(JS::HandleId name, Just HandleId in XPConnect cpp files, since we should be using namespace JS. Here and below.

https://hg.mozilla.org/integration/mozilla-inbound/rev/99e821df3d61 with that change.