Step 2 in porting disk cache to using FilePath.

base/platform_file.h

 // Copyright (c) 2006-2008 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.
 
 #ifndef BASE_PLATFORM_FILE_H_
 #define BASE_PLATFORM_FILE_H_
 
 #include "build/build_config.h"
 #if defined(OS_WIN)
 #include <windows.h>
 #endif
 
 #include <string>
 
+class FilePath;
+
 namespace base {
 
 #if defined(OS_WIN)
 typedef HANDLE PlatformFile;
 const PlatformFile kInvalidPlatformFileValue = INVALID_HANDLE_VALUE;
 #elif defined(OS_POSIX)
 typedef int PlatformFile;
 const PlatformFile kInvalidPlatformFileValue = -1;
 #endif
 
 enum PlatformFileFlags {
   PLATFORM_FILE_OPEN = 1,
   PLATFORM_FILE_CREATE = 2,
   PLATFORM_FILE_OPEN_ALWAYS = 4,    // May create a new file.
   PLATFORM_FILE_CREATE_ALWAYS = 8,  // May overwrite an old file.
   PLATFORM_FILE_READ = 16,
   PLATFORM_FILE_WRITE = 32,
   PLATFORM_FILE_EXCLUSIVE_READ = 64,  // EXCLUSIVE is opposite of Windows SHARE
   PLATFORM_FILE_EXCLUSIVE_WRITE = 128,
   PLATFORM_FILE_ASYNC = 256,
   PLATFORM_FILE_TEMPORARY = 512,        // Used on Windows only
   PLATFORM_FILE_HIDDEN = 1024,          // Used on Windows only
   PLATFORM_FILE_DELETE_ON_CLOSE = 2048
 };
 
 // Creates or opens the given file. If PLATFORM_FILE_OPEN_ALWAYS is used, and
 // |created| is provided, |created| will be set to true if the file was created
 // or to false in case the file was just opened.
+PlatformFile CreatePlatformFile(const FilePath& name,
+                                int flags,
+                                bool* created);
+// Deprecated.
 PlatformFile CreatePlatformFile(const std::wstring& name,
                                 int flags,
                                 bool* created);
 
 // Closes a file handle
 bool ClosePlatformFile(PlatformFile file);
 
 }  // namespace base
 
 #endif  // BASE_PLATFORM_FILE_H_