cleanup: back out performance hacks amended into previous commit

contrib/perf.py

@@ -525,7 +525,6 b' def perfrevlogrevision(ui, repo, file_, '
             r.clearcaches()
         r._chunkraw(chain[0], chain[-1])
 
-    @util.nogc
     def dodecompress(data, chain):
         if not cache:
             r.clearcaches()

mercurial/revlog.py

@@ -1163,7 +1163,6 b' class revlog(object):'
         return mdiff.textdiff(self.revision(rev1),
                               self.revision(rev2))
 
-    @util.nogc
     def revision(self, nodeorrev, _df=None):
         """return an uncompressed revision of a given node or revision
         number.