Fix Unicode issues in dart2js and dart2dart.

sdk/lib/utf/utf16.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.
 
 
 /**
  * Decodes the UTF-16 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.
  * Set the [replacementCodepoint] to null to throw an ArgumentError
@@ skipping 44 matching lines @@
  * Produce a String from a sequence of UTF-16 encoded bytes. This method always
  * strips a leading BOM. Set the [replacementCodepoint] to null to throw  an
  * ArgumentError rather than replace the bad value. The default
  * value for the [replacementCodepoint] is U+FFFD.
  */
 String decodeUtf16(List<int> bytes, [int offset = 0, int length,
     int replacementCodepoint = UNICODE_REPLACEMENT_CHARACTER_CODEPOINT]) {
   Utf16BytesToCodeUnitsDecoder decoder = new Utf16BytesToCodeUnitsDecoder(bytes,
       offset, length, replacementCodepoint);
   List<int> codeunits = decoder.decodeRest();
-  // TODO is16BitCodeUnit() is used to work around a bug with dart2js
-  // (http://code.google.com/p/dart/issues/detail?id=1357). Consider
-  // removing after this issue is resolved.
-  if (_is16BitCodeUnit()) {
-    return new String.fromCharCodes(codeunits);
-  } else {
-    return new String.fromCharCodes(
-        _utf16CodeUnitsToCodepoints(codeunits, 0, null, replacementCodepoint));
-  }
+  return new String.fromCharCodes(
+      _utf16CodeUnitsToCodepoints(codeunits, 0, null, replacementCodepoint));
 }
 
 /**
  * Produce a String from a sequence of UTF-16BE encoded bytes. This method
  * strips a leading BOM by default, but can be overridden by setting the
  * optional parameter [stripBom] to false. Set the [replacementCodepoint] to
  * null to throw an ArgumentError rather than replace the bad value.
  * The default value for the [replacementCodepoint] is U+FFFD.
  */
 String decodeUtf16be(List<int> bytes, [int offset = 0, int length,
     bool stripBom = true,
     int replacementCodepoint = UNICODE_REPLACEMENT_CHARACTER_CODEPOINT]) {
   List<int> codeunits = (new Utf16beBytesToCodeUnitsDecoder(bytes, offset,
       length, stripBom, replacementCodepoint)).decodeRest();
   // TODO is16BitCodeUnit() is used to work around a bug with dart2js
   // (http://code.google.com/p/dart/issues/detail?id=1357). Consider
   // removing after this issue is resolved.
-  if (_is16BitCodeUnit()) {
-    return new String.fromCharCodes(codeunits);
-  } else {
-    return new String.fromCharCodes(
-        _utf16CodeUnitsToCodepoints(codeunits, 0, null, replacementCodepoint));
-  }
+  return new String.fromCharCodes(
+      _utf16CodeUnitsToCodepoints(codeunits, 0, null, replacementCodepoint));
 }
 
 /**
  * Produce a String from a sequence of UTF-16LE encoded bytes. This method
  * strips a leading BOM by default, but can be overridden by setting the
  * optional parameter [stripBom] to false. Set the [replacementCodepoint] to
  * null to throw an ArgumentError rather than replace the bad value.
  * The default value for the [replacementCodepoint] is U+FFFD.
  */
 String decodeUtf16le(List<int> bytes, [int offset = 0, int length,
     bool stripBom = true,
     int replacementCodepoint = UNICODE_REPLACEMENT_CHARACTER_CODEPOINT]) {
   List<int> codeunits = (new Utf16leBytesToCodeUnitsDecoder(bytes, offset,
       length, stripBom, replacementCodepoint)).decodeRest();
   // TODO is16BitCodeUnit() is used to work around a bug with dart2js
   // (http://code.google.com/p/dart/issues/detail?id=1357). Consider
   // removing after this issue is resolved.
-  if (_is16BitCodeUnit()) {
-    return new String.fromCharCodes(codeunits);
-  } else {
-    return new String.fromCharCodes(
-        _utf16CodeUnitsToCodepoints(codeunits, 0, null, replacementCodepoint));
-  }
+  return new String.fromCharCodes(
+      _utf16CodeUnitsToCodepoints(codeunits, 0, null, replacementCodepoint));
 }
 
 /**
  * Produce a list of UTF-16 encoded bytes. This method prefixes the resulting
  * bytes with a big-endian byte-order-marker.
  */
 List<int> encodeUtf16(String str) =>
     encodeUtf16be(str, true);
 
 /**
@@ skipping 64 matching lines @@
   int end = length != null ? offset + length : utf16EncodedBytes.length;
   return (offset + 2) <= end &&
       utf16EncodedBytes[offset] == UNICODE_UTF_BOM_LO &&
       utf16EncodedBytes[offset + 1] == UNICODE_UTF_BOM_HI;
 }
 
 List<int> _stringToUtf16CodeUnits(String str) {
   // TODO is16BitCodeUnit() is used to work around a bug with dart2js
   // (http://code.google.com/p/dart/issues/detail?id=1357). Consider
   // removing after this issue is resolved.
-  if (_is16BitCodeUnit()) {
-    return str.charCodes;
-  } else {
-    return _codepointsToUtf16CodeUnits(str.charCodes);
-  }
+  return _codepointsToUtf16CodeUnits(str.charCodes);
 }
 
 typedef _ListRangeIterator _CodeUnitsProvider();
 
 /**
  * Return type of [decodeUtf16AsIterable] and variants. The Iterable type
  * provides an iterator on demand and the iterator will only translate bytes
  * as requested by the user of the iterator. (Note: results are not cached.)
  */
 class IterableUtf16Decoder implements Iterable<int> {
@@ skipping 124 matching lines @@
       skip();
     }
   }
 
   int decode() {
     int lo = utf16EncodedBytesIterator.next();
     int hi = utf16EncodedBytesIterator.next();
     return (hi << 8) + lo;
   }
 }