Fix argument processing for RandomAccessFile.writeFrom

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 c241a5beb38e80175b88e9a2d5f50bf3bace271c..2fab82d7585082f3fbca4f1a772324c7d95b4b69 100644
--- a/tests/standalone/io/file_test.dart
+++ b/tests/standalone/io/file_test.dart
@@ -716,6 +716,54 @@ class FileTest {
     Expect.isFalse(file.existsSync());
   }
 
+  static void testWriteFrom() async {
+    asyncTestStarted();
+    File file = new File(tempDirectory.path + "/out_write_from");
+
+    var buffer = const [1, 2, 3];
+    var openedFile = await file.open(mode: WRITE);
+
+    await openedFile.writeFrom(buffer);
+    var result = []..addAll(buffer);;
+
+    write([start, end]) async {
+      await openedFile.writeFrom(buffer, start, end);
+      result.addAll(buffer.sublist(start, end));
+    }
+    await write(0, 3);
+    await write(0, 2);
+    await write(1, 2);
+    await write(1, 3);
+    await write(2, 3);
+
+    var bytesFromFile = await file.readAsBytes();
+    Expect.listEquals(result, bytesFromFile);
+    asyncTestDone("testWriteFrom");
+  }
+
+  static void testWriteFromSync() {
+    File file = new File(tempDirectory.path + "/out_write_from_sync");
+
+    var buffer = const [1, 2, 3];
+    var openedFile = file.openSync(mode: WRITE);
+
+    openedFile.writeFromSync(buffer);
+    var result = []..addAll(buffer);;
+
+    write([start, end]) {
+      openedFile.writeFromSync(buffer, start, end);
+      result.addAll(buffer.sublist(start, end));
+    }
+    write(0, 3);
+    write(0, 2);
+    write(1, 2);
+    write(1, 3);
+    write(2, 3);
+
+    var bytesFromFile = file.readAsBytesSync();
+    Expect.listEquals(result, bytesFromFile);
+  }
+
   // Tests exception handling after file was closed.
   static void testCloseException() {
     bool exceptionCaught = false;
@@ -1327,6 +1375,8 @@ class FileTest {
       testPosition();
       testTruncate();
       testTruncateSync();
+      testWriteFrom();
+      testWriteFromSync();
       testCloseException();
       testCloseExceptionStream();
       testBufferOutOfBoundsException();