Backed out changeset b4d189ca8add (bug 1325351) for spidermonkey cgc and plain shell failure in Maybe.h. r=backout

mfbt/Maybe.h

@@ -157,7 +157,13 @@ public:
     if (&aOther != this) {
       if (aOther.mIsSome) {
         if (mIsSome) {
+          // XXX(seth): The correct code for this branch, below, can't be used
+          // due to a bug in Visual Studio 2010. See bug 1052940.
+          /*
           ref() = aOther.ref();
+          */
+          reset();
+          emplace(*aOther);
         } else {
           emplace(*aOther);
         }