bcrypt: benchmark defaults

Currently the benchmarks hard code "10" for the cost but maybe a
better benchmark would be to use the DefaultCost, since this is the
most common use mode for the bcrypt package.

Change-Id: Ie89853fcbe4a3a2830fff812ae5cfe908df145fe
Reviewed-on: https://go-review.googlesource.com/c/144338
Reviewed-by: Filippo Valsorda <filippo@golang.org>

Author: kevinburke

bcrypt/bcrypt_test.go

@@ -209,19 +209,19 @@ func TestMinorNotRequired(t *testing.T) {
 func BenchmarkEqual(b *testing.B) {
 	b.StopTimer()
 	passwd := []byte("somepasswordyoulike")
-	hash, _ := GenerateFromPassword(passwd, 10)
+	hash, _ := GenerateFromPassword(passwd, DefaultCost)
 	b.StartTimer()
 	for i := 0; i < b.N; i++ {
 		CompareHashAndPassword(hash, passwd)
 	}
 }
 
-func BenchmarkGeneration(b *testing.B) {
+func BenchmarkDefaultCost(b *testing.B) {
 	b.StopTimer()
 	passwd := []byte("mylongpassword1234")
 	b.StartTimer()
 	for i := 0; i < b.N; i++ {
-		GenerateFromPassword(passwd, 10)
+		GenerateFromPassword(passwd, DefaultCost)
 	}
 }