[fsp] Let extensions decide about the file system id.

chrome/browser/chromeos/file_system_provider/mount_path_util.h

 // Copyright 2014 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 CHROME_BROWSER_CHROMEOS_FILE_SYSTEM_PROVIDER_MOUNT_PATH_UTIL_H_
 #define CHROME_BROWSER_CHROMEOS_FILE_SYSTEM_PROVIDER_MOUNT_PATH_UTIL_H_
 
 #include <string>
 
 #include "base/files/file_path.h"
 #include "webkit/browser/fileapi/file_system_url.h"
 
 class Profile;
 
 namespace chromeos {
 namespace file_system_provider {
 
 class ProvidedFileSystemInterface;
 
 namespace util {
 
 // Constructs a safe mount point path for the provided file system.
 base::FilePath GetMountPath(Profile* profile,
-                            std::string extension_id,
-                            int file_system_id);
+                            const std::string& extension_id,
+                            const std::string& file_system_id);
 
 // Finds file system, which is responsible for handling the specified |url| by
 // analysing the mount path. Also, extract the file path from the virtual path
 // to be used by the file system operations.
 class FileSystemURLParser {
  public:
   explicit FileSystemURLParser(const fileapi::FileSystemURL& url);
   virtual ~FileSystemURLParser();
 
   // Parses the |url| passed to the constructor. If parsing succeeds, then
   // returns true. Otherwise, false. Must be called on UI thread.
   bool Parse();
 
   ProvidedFileSystemInterface* file_system() const { return file_system_; }
   const base::FilePath& file_path() const { return file_path_; }
 
  private:
   fileapi::FileSystemURL url_;
   ProvidedFileSystemInterface* file_system_;
   base::FilePath file_path_;
 
   DISALLOW_COPY_AND_ASSIGN(FileSystemURLParser);
 };
 
 }  // namespace util
 }  // namespace file_system_provider
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_FILE_SYSTEM_PROVIDER_MOUNT_PATH_UTIL_H_