Bug 419470: Re-enable PGO for Linux mozjemalloc. r=glandium

It only took nine years.

MozReview-Commit-ID: 2zsCBMTJ6O1

--HG--
extra : rebase_source : e3be1bd1c930d32d3c7a9e2d707ed3fe6bc0936f

memory/mozjemalloc/moz.build

@@ -28,11 +28,6 @@ DEFINES['abort'] = 'moz_abort'
 
 DEFINES['MOZ_JEMALLOC_IMPL'] = True
 
-#XXX: PGO on Linux causes problems here
-# See bug 419470
-if CONFIG['OS_TARGET'] == 'Linux':
-    NO_PGO = True
-
 LOCAL_INCLUDES += [
     '/memory/build',
 ]