Move unicode tests to utf package.

pkg/utf/lib/utf32.dart

 // Copyright (c) 2012, 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.
 
 part of utf;
 
 /**
  * Decodes the UTF-32 bytes as an iterable. Thus, the consumer can only convert
  * as much of the input as needed. Determines the byte order from the BOM,
  * or uses big-endian as a default. This method always strips a leading BOM.
@@ skipping 216 matching lines @@
     while (moveNext()) {
       codeunits[i++] = current;
     }
     return codeunits;
   }
 
   int get current => _current;
 
   bool moveNext() {
     _current = null;
-    if (utf32EncodedBytesIterator.remaining < 4) {
+    int remaining = utf32EncodedBytesIterator.remaining;
+    if (remaining == 0) {
+      _current = null;
+      return false;
+    }
+    if (remaining < 4) {
       utf32EncodedBytesIterator.skip(utf32EncodedBytesIterator.remaining);
       if (replacementCodepoint != null) {
           _current = replacementCodepoint;
           return true;
       } else {
         throw new ArgumentError(
             "Invalid UTF32 at ${utf32EncodedBytesIterator.position}");
       }
-    } else {
-      int codepoint = decode();
-      if (_validCodepoint(codepoint)) {
-        _current = codepoint;
-        return true;
-      } else if (replacementCodepoint != null) {
-        _current = replacementCodepoint;
-        return true;
-      } else {
-        throw new ArgumentError(
-            "Invalid UTF32 at ${utf32EncodedBytesIterator.position}");
-      }
     }
+    int codepoint = decode();
+    if (_validCodepoint(codepoint)) {
+      _current = codepoint;
+      return true;
+    } else if (replacementCodepoint != null) {
+      _current = replacementCodepoint;
+      return true;
+    } else {
+      throw new ArgumentError(
+          "Invalid UTF32 at ${utf32EncodedBytesIterator.position}");
+    }
   }
 
   int get position => utf32EncodedBytesIterator.position ~/ 4;
 
   void backup([int by = 1]) {
     utf32EncodedBytesIterator.backup(4 * by);
   }
 
   int get remaining => (utf32EncodedBytesIterator.remaining + 3) ~/ 4;
 
@@ skipping 60 matching lines @@
     value += (utf32EncodedBytesIterator.current << 24);
     return value;
   }
 }
 
 bool _validCodepoint(int codepoint) {
   return (codepoint >= 0 && codepoint < UNICODE_UTF16_RESERVED_LO) ||
       (codepoint > UNICODE_UTF16_RESERVED_HI &&
       codepoint < UNICODE_VALID_RANGE_MAX);
 }