Clean up Linux zygote creation code

content/browser/zygote_host/zygote_communication_linux.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 CONTENT_BROWSER_ZYGOTE_HOST_ZYGOTE_COMMUNICATION_LINUX_H_
 #define CONTENT_BROWSER_ZYGOTE_HOST_ZYGOTE_COMMUNICATION_LINUX_H_
 
 #include <memory>
 #include <set>
 #include <string>
 #include <vector>
 
 #include <sys/types.h>
 
 #include "base/files/scoped_file.h"
 #include "base/process/kill.h"
 #include "base/process/process_handle.h"
 #include "base/synchronization/lock.h"
 #include "content/common/content_export.h"
 #include "content/public/browser/file_descriptor_info.h"
 
 namespace base {
 class Pickle;
 }  // namespace base
 
 namespace content {
 
+// Handles interprocess communication with the Linux zygote process. The zygote
+// does not use standard Chrome IPC or mojo, see:
+// https://chromium.googlesource.com/chromium/src/+/master/docs/linux_sandbox_ipc.md
 class CONTENT_EXPORT ZygoteCommunication {
  public:
   ZygoteCommunication();
   ~ZygoteCommunication();
 
   void Init();
 
   // Tries to start a process of type indicated by process_type.
   // Returns its pid on success, otherwise base::kNullProcessHandle;
   pid_t ForkRequest(const std::vector<std::string>& command_line,
@@ skipping 51 matching lines @@
   base::Lock child_tracking_lock_;
   int sandbox_status_;
   bool have_read_sandbox_status_word_;
   // Set to true when the zygote is initialized successfully.
   bool init_;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_ZYGOTE_HOST_ZYGOTE_COMMUNICATION_LINUX_H_