Fix off-by-one error in UTF-8 encoding.

tests/lib/convert/unicode_tests.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library unicode_tests;
 
 // Google favorite: "Îñţérñåţîöñåļîžåţîờñ".
 const INTER_BYTES = const [0xc3, 0x8e, 0xc3, 0xb1, 0xc5, 0xa3, 0xc3, 0xa9, 0x72,
                            0xc3, 0xb1, 0xc3, 0xa5, 0xc5, 0xa3, 0xc3, 0xae, 0xc3,
                            0xb6, 0xc3, 0xb1, 0xc3, 0xa5, 0xc4, 0xbc, 0xc3, 0xae,
@@ skipping 27 matching lines @@
 
 const DIGIT_BYTES = const [ 0x35 ];
 const DIGIT_STRING = "5";
 
 const ASCII_BYTES = const [ 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68,
                             0x69, 0x6A, 0x6B, 0x6C, 0x6D, 0x6E, 0x6F, 0x70,
                             0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78,
                             0x79, 0x7A ];
 const ASCII_STRING = "abcdefghijklmnopqrstuvwxyz";
 
+const BIGGEST_ASCII_BYTES = const [ 0x7F ];
+const BIGGEST_ASCII_STRING = "\x7F";
+
+const SMALLEST_2_UTF8_UNIT_BYTES = const [ 0xC2, 0x80 ];
+const SMALLEST_2_UTF8_UNIT_STRING = "\u{80}";
+
+const BIGGEST_2_UTF8_UNIT_BYTES = const [ 0xDF, 0xBF ];
+const BIGGEST_2_UTF8_UNIT_STRING = "\u{7FF}";
+
+const SMALLEST_3_UTF8_UNIT_BYTES = const [ 0xE0, 0xA0, 0x80 ];
+const SMALLEST_3_UTF8_UNIT_STRING = "\u{800}";
+
+const BIGGEST_3_UTF8_UNIT_BYTES = const [ 0xEF, 0xBF, 0xBF ];
+const BIGGEST_3_UTF8_UNIT_STRING = "\u{FFFF}";
+
+const SMALLEST_4_UTF8_UNIT_BYTES = const [ 0xF0, 0x90, 0x80, 0x80 ];
+const SMALLEST_4_UTF8_UNIT_STRING = "\u{10000}";
+
 const _TEST_PAIRS = const [
     const [ const [], "" ],
     const [ INTER_BYTES, INTER_STRING ],
     const [ BLUEBERRY_BYTES, BLUEBERRY_STRING ],
     const [ SIVA_BYTES1, SIVA_STRING1 ],
     const [ SIVA_BYTES2, SIVA_STRING2 ],
     const [ BEE_BYTES, BEE_STRING ],
     const [ DIGIT_BYTES, DIGIT_STRING ],
-    const [ ASCII_BYTES, ASCII_STRING ]];
+    const [ ASCII_BYTES, ASCII_STRING ],
+    const [ BIGGEST_ASCII_BYTES, BIGGEST_ASCII_STRING ],
+    const [ SMALLEST_2_UTF8_UNIT_BYTES, SMALLEST_2_UTF8_UNIT_STRING ],
+    const [ BIGGEST_2_UTF8_UNIT_BYTES, BIGGEST_2_UTF8_UNIT_STRING ],
+    const [ SMALLEST_3_UTF8_UNIT_BYTES, SMALLEST_3_UTF8_UNIT_STRING ],
+    const [ BIGGEST_3_UTF8_UNIT_BYTES, BIGGEST_3_UTF8_UNIT_STRING ],
+    const [ SMALLEST_4_UTF8_UNIT_BYTES, SMALLEST_4_UTF8_UNIT_STRING ],
+    ];
 
 List<List> _expandTestPairs() {
   assert(2 == BEE_STRING.length);
   var tests = [];
   tests.addAll(_TEST_PAIRS);
   tests.addAll(_TEST_PAIRS.expand((test) {
     var bytes = test[0];
     var string = test[1];
     var longBytes = [];
     var longString = "";
     for (int i = 0; i < 100; i++) {
       longBytes.addAll(bytes);
       longString += string;
     }
     return [test, [longBytes, longString]];
   }));
   return tests;
 }
 
 final List UNICODE_TESTS = _expandTestPairs();