Add a --no-zygote command line flag

content/browser/child_process_launcher.cc

 // Copyright 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 "content/browser/child_process_launcher.h"
 
 #include <memory>
 #include <utility>
 
 #include "base/bind.h"
@@ skipping 241 matching lines @@
       cmd_line->argv(), child_process_id, std::move(files_to_register), regions,
       base::Bind(&OnChildProcessStartedAndroid, callback, client_thread_id,
                  begin_launch_time, base::Passed(&ipcfd),
                  base::Passed(&mojo_fd)));
 
 #elif defined(OS_POSIX)
   // We need to close the client end of the IPC channel to reliably detect
   // child termination.
 
 #if !defined(OS_MACOSX)
-  ZygoteHandle* zygote_handle = delegate->GetZygote();
+  ZygoteHandle* zygote_handle =
+      !base::CommandLine::ForCurrentProcess()->HasSwitch(switches::kNoZygote)
+          ? delegate->GetZygote()
+          : nullptr;
   // If |zygote_handle| is null, a zygote should not be used.
   if (zygote_handle) {
     // This code runs on the PROCESS_LAUNCHER thread so race conditions are not
     // an issue with the lazy initialization.
     if (*zygote_handle == nullptr) {
       *zygote_handle = CreateZygote();
     }
     zygote = *zygote_handle;
     base::ProcessHandle handle = zygote->ForkRequest(
         cmd_line->argv(), std::move(files_to_register), process_type);
@@ skipping 345 matching lines @@
 }
 
 ChildProcessLauncher::Client* ChildProcessLauncher::ReplaceClientForTest(
     Client* client) {
   Client* ret = client_;
   client_ = client;
   return ret;
 }
 
 }  // namespace content