Charset: Fix broken test for utf8_decode() fallback.

Detected while fuzz-testing the UTF-8 handling code, this defect meant that the tests were verifying the wrong behavior. Namely, they verified a stringification of ASCII digits, which always converted plainly, when they were meant to test handling of invalid UTF-8 sequences.

This patch fixes the test by calling `chr()` on the byte values before concatenating into a big string.

Developed in: WordPress#12147
Discussed in: https://core.trac.wordpress.org/ticket/65372

Props dmsnell, jonsurrell.
Follow-up to: [60950].
See #65372.


git-svn-id: https://develop.svn.wordpress.org/trunk@62484 602fd350-edb4-49c9-b593-d223f7449a82

Author: dmsnell

tests/phpunit/tests/formatting/deprecatedUtfEncodeDecode.php

@@ -68,9 +68,9 @@ public function test_utf8_decode_characters() {
 				 * Since the UTF-16 surrogate halves are not valid Unicode characters,
 				 * these have to be manually constructed as invalid UTF-8.
 				 */
-				$byte1 = 0xE0 | ( $i >> 12 );
-				$byte2 = 0x80 | ( ( $i >> 6 ) & 0x3F );
-				$byte3 = 0x80 | ( $i & 0x3F );
+				$byte1 = chr( 0xE0 | ( $i >> 12 ) );
+				$byte2 = chr( 0x80 | ( ( $i >> 6 ) & 0x3F ) );
+				$byte3 = chr( 0x80 | ( $i & 0x3F ) );
 
 				$c = "{$byte1}{$byte2}{$byte3}";
 			}