Make File.readSync return only the bytes read

tests/standalone/io/file_test.dart

Index: tests/standalone/io/file_test.dart
diff --git a/tests/standalone/io/file_test.dart b/tests/standalone/io/file_test.dart
index 0c7e4f0388b0d87a81bc368d2cb6f0385fb2936c..ad5f2fcbe16775aabda15413b23deeb7ed9b524c 100644
--- a/tests/standalone/io/file_test.dart
+++ b/tests/standalone/io/file_test.dart
@@ -244,6 +244,17 @@ class FileTest {
     Expect.equals(103, buffer[9]);  // represents 'g' in the file.
     Expect.equals(104, buffer[10]);  // represents 'h' in the file.
     Expect.equals(116, buffer[11]);  // represents 't' in the file.
+
+    filename = getFilename("tests/vm/data/fixed_length_file");
+    file = new File(filename);
+    int len = file.lengthSync();
+    Expect.equals(0, file.openSync().readSync(0).length);
+    Expect.equals(1, file.openSync().readSync(1).length);
+    Expect.equals(len - 1, file.openSync().readSync(len - 1).length);
+    Expect.equals(len, file.openSync().readSync(len).length);
+    Expect.equals(len, file.openSync().readSync(len + 1).length);
+    Expect.equals(len, file.openSync().readSync(len * 2).length);
+    Expect.equals(len, file.openSync().readSync(len * 10).length);
   }
 
   // Test for file read and write functionality.