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

tests/standalone/io/file_test.dart

Index: tests/standalone/io/file_test.dart
===================================================================
--- tests/standalone/io/file_test.dart	(revision 24537)
+++ tests/standalone/io/file_test.dart	(working copy)
@@ -529,11 +529,11 @@
         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.