Fix assertion not holding (calling with start==end) and typo.

tests/lib/convert/json_utf8_chunk_test.dart

 // Copyright (c) 2014, 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 test;
 
 import "package:expect/expect.dart";
 import "dart:convert";
 import "unicode_tests.dart" show UNICODE_TESTS;
 
@@ skipping 218 matching lines @@
         sink.add(codes.sublist(i, j));
         sink.add(codes.sublist(j));
         sink.close();
       });
     }
   }
 }
 
 // Test that `codeString.codeUnits` fails to parse as UTF-8 JSON,
 // even with decoder not throwing on malformed encodings.
-void jsonThrows(Strig name, String codeString) {
+void jsonThrows(String name, String codeString) {
   testJsonThrows(tag, action) {
     // Not allowing malformed, expect throw.
     var sink = new ChunkedConversionSink.withCallback((values) {
       Expect.unreachable(tag);
     });
     var decoderSink = JSON.decoder.startChunkedConversion(sink)
                                   .asUtf8Sink(true);
     Expect.throws(() { action(decoderSink); }, null, tag);
   }
 
@@ skipping 191 matching lines @@
           sink.add(bytes.sublist(0, i));
           sink.add(bytes.sublist(i, j));
           sink.add(bytes.sublist(j));
           sink.add([0x22]);
           sink.close();
         });
       }
     }
   }
 }