Dart: Merge message pipe query and read into one native call

mojo/public/dart/mojo/lib/src/codec.dart

Index: mojo/public/dart/mojo/lib/src/codec.dart
diff --git a/mojo/public/dart/mojo/lib/src/codec.dart b/mojo/public/dart/mojo/lib/src/codec.dart
index 020312b152b1590290221aebadd2ccf42d79364f..0332ef3a3a53e59fcc40f8c0ef510ee056ef997a 100644
--- a/mojo/public/dart/mojo/lib/src/codec.dart
+++ b/mojo/public/dart/mojo/lib/src/codec.dart
@@ -105,7 +105,8 @@ class Encoder {
     return result;
   }
 
-  Message get message => new Message(_buffer.trimmed, _buffer.handles);
+  Message get message => new Message(
+      _buffer.trimmed, _buffer.handles, _buffer.extent, _buffer.handles.length);
 
   void encodeStructDataHeader(StructDataHeader dataHeader) {
     _buffer.claimMemory(align(dataHeader.size));
@@ -561,8 +562,7 @@ class Decoder {
 
   Decoder(this._message, [this._base = 0, this._validator = null]) {
     if (_validator == null) {
-      _validator = new _Validator(
-          _message.buffer.lengthInBytes, _message.handles.length);
+      _validator = new _Validator(_message.dataLength, _message.handlesLength);
     }
   }
 
@@ -574,9 +574,13 @@ class Decoder {
 
   ByteData get _buffer => _message.buffer;
   List<core.MojoHandle> get _handles => _message.handles;
-  List<core.MojoHandle> get excessHandles => new List.from(_message.handles
-      .getRange(_validator._minNextClaimedHandle, _message.handles.length))
-    ..addAll(_validator._skippedIndices.map((i) => _message.handles[i]));
+  List<core.MojoHandle> get excessHandles {
+    if (_message.handlesLength == 0) return null;
+    var leftAtEnd = _message.handles
+        .getRange(_validator._minNextClaimedHandle, _message.handlesLength);
+    var skipped = _validator._skippedIndices.map((i) => _message.handles[i]);
+    return new List.from(leftAtEnd)..addAll(skipped);
+  }
 
   int decodeInt8(int offset) => _buffer.getInt8(_base + offset);
   int decodeUint8(int offset) => _buffer.getUint8(_base + offset);
@@ -760,7 +764,7 @@ class Decoder {
     var header = d.decodeDataHeaderForArray(elementSize, expectedLength);
     return arrayViewer(d._buffer.buffer,
         d._buffer.offsetInBytes + d._base + ArrayDataHeader.kHeaderSize,
-        header.numElements);
+        header.numElements).toList();
   }
 
   List<int> decodeInt8Array(int offset, int nullability, int expectedLength) =>
@@ -860,16 +864,13 @@ class Decoder {
           (d, o, n) => d.decodeServiceInterface(o, n, clientFactory), offset,
           kSerializedInterfaceSize, nullability, expectedLength);
 
-  static String _stringOfUtf8(Uint8List bytes) =>
-      (const Utf8Decoder()).convert(bytes.toList());
-
   String decodeString(int offset, bool nullable) {
     int nullability = nullable ? kArrayNullable : 0;
     var bytes = decodeUint8Array(offset, nullability, kUnspecifiedArrayLength);
     if (bytes == null) {
       return null;
     }
-    return _stringOfUtf8(bytes);
+    return (const Utf8Decoder()).convert(bytes);
   }
 
   StructDataHeader decodeDataHeaderForMap() {