Improve process launch handle sharing API.

sandbox/linux/suid/client/setuid_sandbox_host.h

 // Copyright 2015 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 SANDBOX_LINUX_SUID_CLIENT_SETUID_SANDBOX_HOST_H_
 #define SANDBOX_LINUX_SUID_CLIENT_SETUID_SANDBOX_HOST_H_
 
 #include <memory>
 
 #include "base/files/file_path.h"
@@ skipping 32 matching lines @@
   // CHROME_DEVEL_SANDBOX environment variable used for user-managed builds. If
   // the sandbox binary cannot be found, it will return an empty FilePath.
   base::FilePath GetSandboxBinaryPath();
 
   // Modify |cmd_line| to launch via the setuid sandbox. Crash if the setuid
   // sandbox binary cannot be found.  |cmd_line| must not be NULL.
   void PrependWrapper(base::CommandLine* cmd_line);
 
   // Set-up the launch options for launching via the setuid sandbox.  Caller is
   // responsible for keeping |dummy_fd| alive until LaunchProcess() completes.
-  // |options| and |fds_to_remap| must not be NULL.
+  // |options| must not be NULL. This function will append to
+  // options->fds_to_remap so the caller should take care to append rather than
+  // overwrite if it has additional FDs.
   // (Keeping |dummy_fd| alive is an unfortunate historical artifact of the
   // chrome-sandbox ABI.)
   void SetupLaunchOptions(base::LaunchOptions* options,
-                          base::FileHandleMappingVector* fds_to_remap,
                           base::ScopedFD* dummy_fd);
 
   // Set-up the environment. This should be done prior to launching the setuid
   // helper.
   void SetupLaunchEnvironment();
 
  private:
   explicit SetuidSandboxHost(std::unique_ptr<base::Environment> env);
 
   // Holds the environment. Will never be NULL.
   std::unique_ptr<base::Environment> env_;
 
   DISALLOW_COPY_AND_ASSIGN(SetuidSandboxHost);
 };
 
 }  // namespace sandbox
 
 #endif  // SANDBOX_LINUX_SUID_CLIENT_SETUID_SANDBOX_HOST_H_