Make writes consistent across socket and file synchronous/asynchronus writes in terms of truncation…

tests/standalone/io/file_test.dart

 // Copyright (c) 2013, 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.
 //
 // Dart test program for testing file I/O.
 
 import "package:expect/expect.dart";
 import 'dart:async';
 import 'dart:collection';
 import 'dart:io';
@@ skipping 511 matching lines @@
     final File file = new File(fileName);
     file.create().then((ignore) {
       file.open(mode: WRITE).then((RandomAccessFile openedFile) {
         // Write bytes from 0 to 7.
         openedFile.writeFrom([0], 0, 1);
         openedFile.writeFrom(const [1], 0, 1);
         openedFile.writeFrom(new MyListOfOneElement(2), 0, 1);
         var x = 12345678901234567890123456789012345678901234567890;
         var y = 12345678901234567890123456789012345678901234567893;
         openedFile.writeFrom([y - x], 0, 1);
-        openedFile.writeFrom([260], 0, 1);  // 260 = 256 + 4 = 0x104.

[Anders Johnsen, 2013/06/28 05:21:48]

If this is illegal now, please add a test for it.

[siva, 2013/06/28 18:44:56]

Writing values > 255 throws an ArgumentError which is what the socket write
function was doing. So this behaviour is now
replicated to the file write function also for consistency.

I will add a negative test which ensures that an ArgumentError is
thrown if values > 255 are written.

-        openedFile.writeFrom(const [261], 0, 1);
-        openedFile.writeFrom(new MyListOfOneElement(262), 0, 1);
+        openedFile.writeFrom([4], 0, 1);
+        openedFile.writeFrom(const [5], 0, 1);
+        openedFile.writeFrom(new MyListOfOneElement(6), 0, 1);
         x = 12345678901234567890123456789012345678901234567890;
-        y = 12345678901234567890123456789012345678901234568153;
+        y = 12345678901234567890123456789012345678901234567897;
         openedFile.writeFrom([y - x], 0, 1).then((ignore) {
           openedFile.close().then((ignore) {
             // Check the written bytes.
             final File file2 = new File(fileName);
             var openedFile2 = file2.openSync();
             var length = openedFile2.lengthSync();
             Expect.equals(8, length);
             List data = new List(length);
             openedFile2.readIntoSync(data, 0, length);
             for (var i = 0; i < data.length; i++) {
@@ skipping 784 matching lines @@
       testWriteStringUtf8Sync();
       testRename();
       testRenameSync();
     });
   }
 }
 
 main() {
   FileTest.testMain();
 }