Adds blocking file locks.

runtime/bin/file.h

 // 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.
 
 #ifndef BIN_FILE_H_
 #define BIN_FILE_H_
 
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ skipping 63 matching lines @@
     kSize = 5,
     kStatSize = 6
   };
 
   enum LockType {
     // These match the constants in FileStat in file_impl.dart.
     kLockMin = 0,
     kLockUnlock = 0,
     kLockShared = 1,
     kLockExclusive = 2,
-    kLockMax = 2
+    kLockBlockingShared = 3,
+    kLockBlockingExclusive = 4,
+    kLockMax = 4
   };
 
   intptr_t GetFD();
 
   void* MapExecutable(intptr_t* num_bytes);
 
   // Read/Write attempt to transfer num_bytes to/from buffer. It returns
   // the number of bytes read/written.
   int64_t Read(void* buffer, int64_t num_bytes);
   int64_t Write(const void* buffer, int64_t num_bytes);
@@ skipping 137 matching lines @@
   Dart_WeakPersistentHandle weak_handle_;
 
   friend class ReferenceCounted<File>;
   DISALLOW_COPY_AND_ASSIGN(File);
 };
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // BIN_FILE_H_