Fix coded buffer reader so all tests pass using dart2js.

lib/src/protobuf/coded_buffer_reader.dart

 // Copyright (c) 2011, 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 protobuf;
 
 class CodedBufferReader {
   static const int DEFAULT_RECURSION_LIMIT = 64;
   static const int DEFAULT_SIZE_LIMIT = 64 << 20;
 
   final Uint8List _buffer;
   int _bufferPos = 0;
   int _currentLimit = -1;
   int _lastTag = 0;
   int _recursionDepth = 0;
   final int _recursionLimit;
   final int _sizeLimit;
 
-  CodedBufferReader(
-      List<int> buffer,
+  CodedBufferReader(List<int> buffer,
       {int recursionLimit: DEFAULT_RECURSION_LIMIT,
-      int sizeLimit: DEFAULT_SIZE_LIMIT}) :
-      _buffer =
-          buffer is Uint8List
-            ? buffer
-            : new Uint8List(buffer.length)..setRange(0, buffer.length, buffer),
-      _recursionLimit = recursionLimit,
-      _sizeLimit = math.min(sizeLimit, buffer.length) {
+      int sizeLimit: DEFAULT_SIZE_LIMIT})
+      : _buffer = buffer is Uint8List ? buffer : new Uint8List(buffer.length)
+          ..setRange(0, buffer.length, buffer),
+        _recursionLimit = recursionLimit,
+        _sizeLimit = math.min(sizeLimit, buffer.length) {
     _currentLimit = _sizeLimit;
   }
 
   void checkLastTagWas(int value) {
     if (_lastTag != value) {
       throw new InvalidProtocolBufferException.invalidEndTag();
     }
   }
 
   bool isAtEnd() => _bufferPos >= _currentLimit;
@@ skipping 16 matching lines @@
 
   void _checkLimit(int increment) {
     assert(_currentLimit != -1);
     _bufferPos += increment;
     if (_bufferPos > _currentLimit) {
       throw new InvalidProtocolBufferException.truncatedMessage();
     }
   }
 
   void readGroup(int fieldNumber, GeneratedMessage message,
-                 ExtensionRegistry extensionRegistry) {
+      ExtensionRegistry extensionRegistry) {
     if (_recursionDepth >= _recursionLimit) {
       throw new InvalidProtocolBufferException.recursionLimitExceeded();
     }
     ++_recursionDepth;
     message.mergeFromCodedBufferReader(this, extensionRegistry);
     checkLastTagWas(makeTag(fieldNumber, WIRETYPE_END_GROUP));
     --_recursionDepth;
   }
 
   UnknownFieldSet readUnknownFieldSetGroup(int fieldNumber) {
     if (_recursionDepth >= _recursionLimit) {
       throw new InvalidProtocolBufferException.recursionLimitExceeded();
     }
     ++_recursionDepth;
     UnknownFieldSet unknownFieldSet = new UnknownFieldSet();
     unknownFieldSet.mergeFromCodedBufferReader(this);
     checkLastTagWas(makeTag(fieldNumber, WIRETYPE_END_GROUP));
     --_recursionDepth;
     return unknownFieldSet;
   }
 
-  void readMessage(GeneratedMessage message,
-                   ExtensionRegistry extensionRegistry) {
+  void readMessage(
+      GeneratedMessage message, ExtensionRegistry extensionRegistry) {
     int length = readInt32();
     if (_recursionDepth >= _recursionLimit) {
       throw new InvalidProtocolBufferException.recursionLimitExceeded();
     }
     if (length < 0) {
       throw new ArgumentError(
           'CodedBufferReader encountered an embedded string or message'
           ' which claimed to have negative size.');
     }
 
@@ skipping 17 matching lines @@
   int readSint32() => _decodeZigZag32(readUint32());
   Int64 readSint64() => _decodeZigZag64(readUint64());
   int readFixed32() => _readByteData(4).getUint32(0, Endianness.LITTLE_ENDIAN);
   Int64 readFixed64() => readSfixed64();
   int readSfixed32() => _readByteData(4).getInt32(0, Endianness.LITTLE_ENDIAN);
   Int64 readSfixed64() {
     var data = _readByteData(8);
     var view = new Uint8List.view(data.buffer, data.offsetInBytes, 8);
     return new Int64.fromBytes(view);
   }
+
   bool readBool() => _readRawVarint32() != 0;
   List<int> readBytes() {
     int length = readInt32();
     _checkLimit(length);
-    return new Uint8List.view(_buffer.buffer,
-        _buffer.offsetInBytes + _bufferPos - length, length);
+    return new Uint8List.view(
+        _buffer.buffer, _buffer.offsetInBytes + _bufferPos - length, length);
   }
+
   String readString() => _UTF8.decode(readBytes());
   double readFloat() =>
       _readByteData(4).getFloat32(0, Endianness.LITTLE_ENDIAN);
   double readDouble() =>
       _readByteData(8).getFloat64(0, Endianness.LITTLE_ENDIAN);
 
   int readTag() {
     if (isAtEnd()) {
       _lastTag = 0;
       return 0;
     }
 
     _lastTag = readInt32();
     if (getTagFieldNumber(_lastTag) == 0) {
       throw new InvalidProtocolBufferException.invalidTag();
     }
     return _lastTag;
   }
 
   static int _decodeZigZag32(int value) {
-    if ((value & 0x1) == 1) value = -value;
-    return value >> 1;
+    if ((value & 0x1) == 1) {
+      return -(value >> 1) - 1;
+    } else {
+      return value >> 1;
+    }
   }
 
   static Int64 _decodeZigZag64(Int64 value) {
     if ((value & 0x1) == 1) value = -value;
     return value >> 1;
   }
 
   int _readRawVarintByte() {
     _checkLimit(1);
     return _buffer[_bufferPos - 1];
@@ skipping 43 matching lines @@
     }
     throw new InvalidProtocolBufferException.malformedVarint();
   }
 
   ByteData _readByteData(int sizeInBytes) {
     _checkLimit(sizeInBytes);
     return new ByteData.view(_buffer.buffer,
         _buffer.offsetInBytes + _bufferPos - sizeInBytes, sizeInBytes);
   }
 }