bufio: add example for Scanner.Bytes

Change-Id: I4a5c7573e13dd85531ee9f4dd2a0d1981bf8cdfa
Reviewed-on: https://go-review.googlesource.com/c/go/+/51412
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/bufio/example_test.go

@@ -31,6 +31,16 @@ func ExampleScanner_lines() {
 	}
 }
 
+// Use return the most recent call to Scan as a []byte
+func ExampleScanner_Bytes() {
+	scanner := bufio.NewScanner(strings.NewReader("gopher"))
+	for scanner.Scan() {
+		fmt.Println(len(scanner.Bytes()) == 6)
+	}
+	// Output:
+	// true
+}
+
 // Use a Scanner to implement a simple word-count utility by scanning the
 // input as a sequence of space-delimited tokens.
 func ExampleScanner_words() {