Make it an error to call close twice on a file using the async API.

runtime/bin/file_impl.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.
 
 class _FileInputStream extends _BaseDataInputStream implements InputStream {
   _FileInputStream(String name) {
     _file = new File(name);
     _data = [];
     _position = 0;
     _file.onError = (e) {
@@ skipping 685 matching lines @@
   String _name;
 
   SendPort _fileService;
 }
 
 
 class _RandomAccessFile extends _FileBase implements RandomAccessFile {
   _RandomAccessFile(int this._id, String this._name);
 
   void close(void callback()) {
-    if (_id == 0) return;
+    if (_id == 0) {
+      if (_onError != null) {
+        _onError(new FileIOException("Cannot close file: $_name"));
+      }
+      return;
+    }
     _ensureFileService();
     List request = new List(2);
     request[0] = _FileUtils.kCloseRequest;
     request[1] = _id;
     // Set the id_ to 0 (NULL) to ensure the no more async requests
     // can be issues for this file.
     _id = 0;
     _fileService.call(request).then((result) {
       if (result != -1) {
         _id = result;
         callback();
       } else if (_onError != null) {
-        _onError("Cannot close file: $_name");
+        _onError(new FileIOException("Cannot close file: $_name"));
       }
     });
   }
 
   void closeSync() {
     var id = _FileUtils.close(_id);
     if (id == -1) {
       throw new FileIOException("Cannot close file: $_name");
     }
     _id = id;
@@ skipping 20 matching lines @@
       throw new FileIOException("readByte failed", result);
     }
     return result;
   }
 
   void readList(List<int> buffer, int offset, int bytes,
                 void callback(int read)) {
     _ensureFileService();
     if (buffer is !List || offset is !int || bytes is !int) {
       if (_onError != null) {
-        _onError("Invalid arguments to readList");
+        _onError(new FileIOException("Invalid arguments to readList"));
       }
       return;
     };
     List request = new List(3);
     request[0] = _FileUtils.kReadListRequest;
     request[1] = _id;
     request[2] = bytes;
     _fileService.call(request).then((response) {
       if (_isErrorResponse(response)) {
         _reportError(response, "readList failed");
@@ skipping 21 matching lines @@
     if (result is OSError) {
       throw new FileIOException("readList failed", result);
     }
     return result;
   }
 
   void writeByte(int value) {
     _ensureFileService();
     if (value is !int) {
       if (_onError != null) {
-        _onError("Invalid argument to writeByte");
+        _onError(new FileIOException("Invalid argument to writeByte"));
       }
       return;
     }
     List request = new List(3);
     request[0] = _FileUtils.kWriteByteRequest;
     request[1] = _id;
     request[2] = value;
     _writeEnqueued();
     _fileService.call(request).then((response) {
       _writeCompleted();
@@ skipping 12 matching lines @@
     if (result is OSError) {
       throw new FileIOException("writeByte failed", result);
     }
     return result;
   }
 
   void writeList(List<int> buffer, int offset, int bytes) {
     _ensureFileService();
     if (buffer is !List || offset is !int || bytes is !int) {
       if (_onError != null) {
-        _onError("Invalid arguments to writeList");
+        _onError(new FileIOException("Invalid arguments to writeList"));
       }
       return;
     }
 
     List result =
         _FileUtils.ensureFastAndSerializableBuffer(buffer, offset, bytes);
     List outBuffer = result[0];
     int outOffset = result[1];
 
     List request = new List(5);
@@ skipping 208 matching lines @@
   String _name;
   int _id;
   int _pendingWrites = 0;
 
   SendPort _fileService;
 
   Timer _noPendingWriteTimer;
 
   Function _onNoPendingWrites;
 }