Bug 1325351 part 1 - Remove workaround for VS2010 in Maybe. r=froydnj

MozReview-Commit-ID: Anlrf3D2WtN

--HG--
extra : rebase_source : a90c32e397c5081e51e6c2461d045591afae9320

mfbt/Maybe.h

@@ -157,13 +157,7 @@ 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);
         }