bytes: improve readability of IndexAny and LastIndexAny functions

This change removes the check of len(chars) > 0 inside the Index and
IndexAny functions which was redundant.

Change-Id: Ic4bf8b8a37d7f040d3ebd81b4fc45fcb386b639a
Reviewed-on: https://go-review.googlesource.com/65851
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/bytes/bytes.go

@@ -144,7 +144,6 @@ func IndexRune(s []byte, r rune) int {
 // code points in chars. It returns -1 if chars is empty or if there is no code
 // point in common.
 func IndexAny(s []byte, chars string) int {
-	if len(chars) > 0 {
 	if len(s) > 8 {
 		if as, isASCII := makeASCIISet(chars); isASCII {
 			for i, c := range s {
@@ -169,7 +168,6 @@ func IndexAny(s []byte, chars string) int {
 			}
 		}
 	}
-	}
 	return -1
 }
 
@@ -178,7 +176,6 @@ func IndexAny(s []byte, chars string) int {
 // the Unicode code points in chars. It returns -1 if chars is empty or if
 // there is no code point in common.
 func LastIndexAny(s []byte, chars string) int {
-	if len(chars) > 0 {
 	if len(s) > 8 {
 		if as, isASCII := makeASCIISet(chars); isASCII {
 			for i := len(s) - 1; i >= 0; i-- {
@@ -198,7 +195,6 @@ func LastIndexAny(s []byte, chars string) int {
 			}
 		}
 	}
-	}
 	return -1
 }