Update from https://crrev.com/312600

base/process/launch.h

 // Copyright 2013 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.
 
 // This file contains functions for launching subprocesses.
 
 #ifndef BASE_PROCESS_LAUNCH_H_
 #define BASE_PROCESS_LAUNCH_H_
 
 #include <string>
@@ skipping 273 matching lines @@
 // Look up the bootstrap server named |replacement_bootstrap_name| via the
 // current |bootstrap_port|. Then replace the task's bootstrap port with the
 // received right.
 void ReplaceBootstrapPort(const std::string& replacement_bootstrap_name);
 #endif  // defined(OS_MACOSX)
 
 // Creates a LaunchOptions object suitable for launching processes in a test
 // binary. This should not be called in production/released code.
 BASE_EXPORT LaunchOptions LaunchOptionsForTest();
 
+#if defined(OS_LINUX)
+// A wrapper for clone with fork-like behavior, meaning that it returns the
+// child's pid in the parent and 0 in the child. |flags|, |ptid|, and |ctid| are
+// as in the clone system call (the CLONE_VM flag is not supported).
+//
+// This function uses the libc clone wrapper (which updates libc's pid cache)
+// internally, so callers may expect things like getpid() to work correctly
+// after in both the child and parent. An exception is when this code is run
+// under Valgrind. Valgrind does not support the libc clone wrapper, so the libc
+// pid cache may be incorrect after this function is called under Valgrind.
+//
+// As with fork(), callers should be extremely careful when calling this while
+// multiple threads are running, since at the time the fork happened, the
+// threads could have been in any state (potentially holding locks, etc.).
+// Callers should most likely call execve() in the child soon after calling
+// this.
+BASE_EXPORT pid_t ForkWithFlags(unsigned long flags, pid_t* ptid, pid_t* ctid);
+#endif
+
 }  // namespace base
 
 #endif  // BASE_PROCESS_LAUNCH_H_