On compilers that don't support enum class, we define it as a class and define our own constructors. These override the default constructors, so Enum res; no longer works. We need a default constructor with zero arguments that does nothing.
Created attachment 652067 [details] [diff] [review] Patch
Green try: https://tbpl.mozilla.org/?tree=Try&rev=8d6b61bf89ac https://hg.mozilla.org/integration/mozilla-inbound/rev/88b802832f52
Backed out for Android builds failures: https://tbpl.mozilla.org/?tree=Mozilla-Inbound&rev=19ec214f806c https://hg.mozilla.org/integration/mozilla-inbound/rev/22ce0a41fe21
Sorry, was looking at the wrong push. Relanded: https://hg.mozilla.org/integration/mozilla-inbound/rev/7d2db7e3879a