Require FLAG_WRITE when FLAG_CREATE_ALWAYS is specified

base/files/file_win.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/files/file.h"
 
 #include <io.h>
 
 #include "base/files/file_path.h"
 #include "base/logging.h"
@@ skipping 16 matching lines @@
     disposition = CREATE_NEW;
   }
 
   if (flags & FLAG_OPEN_ALWAYS) {
     DCHECK(!disposition);
     disposition = OPEN_ALWAYS;
   }
 
   if (flags & FLAG_CREATE_ALWAYS) {
     DCHECK(!disposition);
+    DCHECK(flags & FLAG_WRITE);
     disposition = CREATE_ALWAYS;
   }
 
   if (flags & FLAG_OPEN_TRUNCATED) {
     DCHECK(!disposition);
     DCHECK(flags & FLAG_WRITE);
     disposition = TRUNCATE_EXISTING;
   }
 
   if (!disposition) {
@@ skipping 292 matching lines @@
                                   last_error);
       return FILE_ERROR_FAILED;
   }
 }
 
 void File::SetPlatformFile(PlatformFile file) {
   file_.Set(file);
 }
 
 }  // namespace base