Support length operation without opening file.

tests/standalone/src/io/FileTest.dart

 // Copyright (c) 2012, 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("dart:io");
 #import("dart:isolate");
 
 class MyListOfOneElement implements List {
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     // Directories should throw exception.
     var file_dir = new File(".");
     Expect.throws(file_dir.directorySync, (e) { return e is FileIOException; });
     file_dir = new File(tempDir);
     Expect.throws(file_dir.directorySync, (e) { return e is FileIOException; });
   }
 
   // Test for file length functionality.
   static void testLength() {
     String filename = getFilename("tests/vm/data/fixed_length_file");
-    RandomAccessFile input = (new File(filename)).openSync();
-    input.onError = (e) => Expect.fail("No errors expected");
-    input.length((length) {
+    File file = new File(filename);
+    RandomAccessFile openedFile = file.openSync();
+    openedFile.onError = (e) => Expect.fail("No errors expected");
+    file.onError = (e) => Expect.fail("No errors expected");
+    openedFile.length((length) {
       Expect.equals(42, length);
-      input.close(() => null);
+      openedFile.close(() => null);
+    });
+    file.length((length) {
+      Expect.equals(42, length);
     });
   }
 
   static void testLengthSync() {
     String filename = getFilename("tests/vm/data/fixed_length_file");
-    RandomAccessFile input = (new File(filename)).openSync();
-    Expect.equals(42, input.lengthSync());
-    input.closeSync();
+    File file = new File(filename);
+    RandomAccessFile openedFile = file.openSync();
+    Expect.equals(42, file.lengthSync());
+    Expect.equals(42, openedFile.lengthSync());
+    openedFile.closeSync();
   }
 
   // Test for file position functionality.
   static void testPosition() {
     String filename = getFilename("tests/vm/data/fixed_length_file");
     RandomAccessFile input = (new File(filename)).openSync();
     input.onError = (e) => Expect.fail("No errors expected");
     input.position((position) {
       Expect.equals(0, position);
       List<int> buffer = new List<int>(100);
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       testWriteVariousLists();
       testDirectory();
       testDirectorySync();
     });
   }
 }
 
 main() {
   FileTest.testMain();
 }