Fix a couple of doc comment references - and many spelling mistakes

sdk/lib/io/http_parser.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;
 
 // Global constants.
 class _Const {
   // Bytes for "HTTP".
   static const HTTP = const [72, 84, 84, 80];
@@ skipping 194 matching lines @@
       // TODO(26379): add test for this branch.
       return new Stream<List<int>>.fromIterable([bufferedData]).listen(onData,
           onError: onError, onDone: onDone, cancelOnError: cancelOnError);
     }
   }
 }
 
 /**
  * HTTP parser which parses the data stream given to [consume].
  *
- * If an HTTP parser error occours, the parser will signal an error to either
+ * If an HTTP parser error occurs, the parser will signal an error to either
  * the current _HttpIncoming or the _parser itself.
  *
  * The connection upgrades (e.g. switching from HTTP/1.1 to the
  * WebSocket protocol) is handled in a special way. If connection
  * upgrade is specified in the headers, then on the callback to
  * [:responseStart:] the [:upgrade:] property on the [:HttpParser:]
  * object will be [:true:] indicating that from now on the protocol is
  * not HTTP anymore and no more callbacks will happen, that is
  * [:dataReceived:] and [:dataEnd:] are not called in this case as
  * there is no more HTTP data. After the upgrade the method
@@ skipping 821 matching lines @@
     }
   }
 
   void _reportError(error, [stackTrace]) {
     if (_socketSubscription != null) _socketSubscription.cancel();
     _state = _State.FAILURE;
     _controller.addError(error, stackTrace);
     _controller.close();
   }
 }