runtime: simplify stack copying in ThreadCreateProfile

Change-Id: I7414d2fab18ae6e7e7c50f8697ec64d38290f409
Reviewed-on: https://go-review.googlesource.com/19817
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/runtime/mprof.go

@@ -506,9 +506,7 @@ func ThreadCreateProfile(p []StackRecord) (n int, ok bool) {
 		ok = true
 		i := 0
 		for mp := first; mp != nil; mp = mp.alllink {
-			for s := range mp.createstack {
-				p[i].Stack0[s] = uintptr(mp.createstack[s])
-			}
+			p[i].Stack0 = mp.createstack
 			i++
 		}
 	}