Stop base::OpenFile from leaking fds/handles into child procs.

base/files/file_util_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_util.h"
 
 #include <windows.h>
 #include <io.h>
 #include <psapi.h>
 #include <shellapi.h>
@@ skipping 52 matching lines @@
       if (recursive && (!DeleteFileRecursive(current, pattern, true) ||
                         !RemoveDirectory(current.value().c_str())))
         return false;
     } else if (!::DeleteFile(current.value().c_str())) {
       return false;
     }
   }
   return true;
 }
 
+// Appends |mode_char| to |mode| before the optional character set encoding; see
+// https://msdn.microsoft.com/library/yeby3zcb.aspx for details.
+void AppendModeCharacter(base::char16 mode_char, base::string16* mode) {
+  size_t comma_pos = mode->find(L',');
+  mode->insert(comma_pos == base::string16::npos ? mode->length() : comma_pos,
+               1, mode_char);
+}
+
 }  // namespace
 
 FilePath MakeAbsoluteFilePath(const FilePath& input) {
   ThreadRestrictions::AssertIOAllowed();
   wchar_t file_path[MAX_PATH];
   if (!_wfullpath(file_path, input.value().c_str(), MAX_PATH))
     return FilePath();
   return FilePath(file_path);
 }
 
@@ skipping 504 matching lines @@
   results->is_directory =
       (attr.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY) != 0;
   results->last_modified = Time::FromFileTime(attr.ftLastWriteTime);
   results->last_accessed = Time::FromFileTime(attr.ftLastAccessTime);
   results->creation_time = Time::FromFileTime(attr.ftCreationTime);
 
   return true;
 }
 
 FILE* OpenFile(const FilePath& filename, const char* mode) {
+  // 'N' is unconditionally added below, so be sure there is not one already
+  // present before a comma in |mode|.
+  DCHECK(
+      strchr(mode, 'N') == nullptr ||
+      (strchr(mode, ',') != nullptr && strchr(mode, 'N') > strchr(mode, ',')));
   ThreadRestrictions::AssertIOAllowed();
   string16 w_mode = ASCIIToUTF16(mode);
+  AppendModeCharacter(L'N', &w_mode);
   return _wfsopen(filename.value().c_str(), w_mode.c_str(), _SH_DENYNO);
 }
 
 FILE* FileToFILE(File file, const char* mode) {
   if (!file.IsValid())
     return NULL;
   int fd =
       _open_osfhandle(reinterpret_cast<intptr_t>(file.GetPlatformFile()), 0);
   if (fd < 0)
     return NULL;
@@ skipping 219 matching lines @@
     // Like Move, this function is not transactional, so we just
     // leave the copied bits behind if deleting from_path fails.
     // If to_path exists previously then we have already overwritten
     // it by now, we don't get better off by deleting the new bits.
   }
   return false;
 }
 
 }  // namespace internal
 }  // namespace base