Fix test warnings and expect Safari mobile simulator bug.

tests/lib/convert/json_utf8_chunk_test.dart

Index: tests/lib/convert/json_utf8_chunk_test.dart
diff --git a/tests/lib/convert/json_utf8_chunk_test.dart b/tests/lib/convert/json_utf8_chunk_test.dart
index 27324ed2ba14c399873e829acdec8e05543b7b49..efa8593df5cadcc3f129917846790b113fee2117 100644
--- a/tests/lib/convert/json_utf8_chunk_test.dart
+++ b/tests/lib/convert/json_utf8_chunk_test.dart
@@ -204,7 +204,7 @@ void jsonMalformedTest(name, expect, codes) {
     }
     {  // Not allowing malformed, expect throw.
       var sink = new ChunkedConversionSink.withCallback((values) {
-        Expect.unreachable(tag);
+        Expect.fail(tag);
       });
       var decoderSink = JSON.decoder.startChunkedConversion(sink)
                                     .asUtf8Sink(false);
@@ -240,7 +240,7 @@ void jsonThrows(String name, String codeString) {
   testJsonThrows(tag, action) {
     // Not allowing malformed, expect throw.
     var sink = new ChunkedConversionSink.withCallback((values) {
-      Expect.unreachable(tag);
+      Expect.fail(tag);
     });
     var decoderSink = JSON.decoder.startChunkedConversion(sink)
                                   .asUtf8Sink(true);