fix spelling in core libraries

sdk/lib/io/file.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.
 
 part of dart.io;
 
 /**
  * The modes in which a File can be opened.
  */
 class FileMode {
@@ skipping 96 matching lines @@
  *     }
  *
  * A more flexible and useful way to read a file is with a [Stream].
  * Open the file with [openRead], which returns a stream that
  * provides the data in the file as chunks of bytes.
  * Listen to the stream for data and process as needed.
  * You can use various transformers in succession to manipulate the
  * data into the required format or to prepare it for output.
  *
  * You might want to use a stream to read large files,
- * to manipulate the data with tranformers,
+ * to manipulate the data with transformers,
  * or for compatibility with another API, such as [WebSocket]s.
  *
  *     import 'dart:io';
  *     import 'dart:convert';
  *     import 'dart:async';
  *
  *     main() {
  *       final file = new File('file.txt');
  *       Stream<List<int>> inputStream = file.openRead();
  *
@@ skipping 451 matching lines @@
    *
    * Throws a [FileSystemException] if the operation fails.
    */
   List<int> readSync(int bytes);
 
   /**
    * Reads into an existing [List<int>] from the file. If [start] is present,
    * the bytes will be filled into [buffer] from at index [start], otherwise
    * index 0. If [end] is present, the [end] - [start] bytes will be read into
    * [buffer], otherwise up to [buffer.length]. If [end] == [start] nothing
-   * happends.
+   * happens.
    *
    * Returns a [:Future<int>:] that completes with the number of bytes read.
    */
   Future<int> readInto(List<int> buffer, [int start = 0, int end]);
 
   /**
    * Synchronously reads into an existing [List<int>] from the file. If [start]
    * is present, the bytes will be filled into [buffer] from at index [start],
    * otherwise index 0.  If [end] is present, the [end] - [start] bytes will be
    * read into [buffer], otherwise up to [buffer.length]. If [end] == [start]
-   * nothing happends.
+   * nothing happens.
    *
    * Throws a [FileSystemException] if the operation fails.
    */
   int readIntoSync(List<int> buffer, [int start = 0, int end]);
 
   /**
    * Writes a single byte to the file. Returns a
    * [:Future<RandomAccessFile>:] that completes with this
    * RandomAccessFile when the write completes.
    */
@@ skipping 279 matching lines @@
       sb.write(": $osError");
       if (path != null) {
         sb.write(", path = '$path'");
       }
     } else if (path != null) {
       sb.write(": $path");
     }
     return sb.toString();
   }
 }