Right now in js/Utility.h we do: |namespace js { using namespace mozilla; }|. This causes problems for js::ion::Range when we try to create and use mozilla::Range, because references to Range in |namespace js { namespace ion { <here> } }| get confused about which Range to use. The best solution for now is to remove the automatic addition of mozilla to js and eat the several extra mozilla:: we need to add to headers.

Comment on attachment 676832 [details] [diff] [review] v0 Review of attachment 676832 [details] [diff] [review]: ----------------------------------------------------------------- Since mfbt stuff's more fundamental than JS stuff, a part of me thinks the |using namespace mozilla| bits should go before the |using js| bits, but perhaps there's more to be said for simple alphabetical order than there is for conceptual correctness.

Green try runs between: https://tbpl.mozilla.org/?tree=Try&rev=bb7f0f419f96 and https://tbpl.mozilla.org/?tree=Try&rev=d586cdd73bab Pushed at: https://hg.mozilla.org/integration/mozilla-inbound/rev/13cf8566804c