[dev.garbage] runtime: remove unused head/end arguments from freeSpan

These used to be used for the list of newly freed objects, but that's
no longer a thing.

Change-Id: I5a4503137b74ec0eae5372ca271b1aa0b32df074
Reviewed-on: https://go-review.googlesource.com/22557Reviewed-by: Rick Hudson <rlh@golang.org>
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/runtime/mcentral.go

@@ -160,7 +160,7 @@ func (c *mcentral) uncacheSpan(s *mspan) {
 // freeSpan returns true if s was returned to the heap.
 // If preserve=true, it does not move s (the caller
 // must take care of it).
-func (c *mcentral) freeSpan(s *mspan, start gclinkptr, end gclinkptr, preserve bool, wasempty bool) bool {
+func (c *mcentral) freeSpan(s *mspan, preserve bool, wasempty bool) bool {
 	if s.incache {
 		throw("freeSpan given cached span")
 	}

src/runtime/mgcsweep.go

@@ -187,8 +187,6 @@ func (s *mspan) sweep(preserve bool) bool {
 	res := false
 	nfree := 0
 
-	var head, end gclinkptr
-
 	c := _g_.m.mcache
 	freeToHeap := false
 
@@ -292,7 +290,7 @@ func (s *mspan) sweep(preserve bool) bool {
 
 	if nfree > 0 && cl != 0 {
 		c.local_nsmallfree[cl] += uintptr(nfree)
-		res = mheap_.central[cl].mcentral.freeSpan(s, head, end, preserve, wasempty)
+		res = mheap_.central[cl].mcentral.freeSpan(s, preserve, wasempty)
 		// MCentral_FreeSpan updates sweepgen
 	} else if freeToHeap {
 		// Free large span to heap