Make hasNext a getter instead of a method.

lib/utf/utf32.dart

Index: lib/utf/utf32.dart
diff --git a/lib/utf/utf32.dart b/lib/utf/utf32.dart
index 31c1bc8c17344d81f620a1e3585f7ca05561641f..9cbfd7aa982e14aabd5262ad3c3c6ac2257b1236 100644
--- a/lib/utf/utf32.dart
+++ b/lib/utf/utf32.dart
@@ -219,13 +219,13 @@ class Utf32BytesDecoder implements _ListRangeIterator {
   List<int> decodeRest() {
     List<int> codeunits = new List<int>(remaining);
     int i = 0;
-    while (hasNext()) {
+    while (hasNext) {
       codeunits[i++] = next();
     }
     return codeunits;
   }
 
-  bool hasNext() => utf32EncodedBytesIterator.hasNext();
+  bool get hasNext => utf32EncodedBytesIterator.hasNext;
 
   int next() {
     if (utf32EncodedBytesIterator.remaining < 4) {