Update from https://crrev.com/312398

base/process/launch.h

Index: base/process/launch.h
diff --git a/base/process/launch.h b/base/process/launch.h
index 6cd02d63cabf3dfe556411c6a8d2202a8a7ffff7..eca4f8f7a44eeb1af2b0625dff6bc3f0b32b60d3 100644
--- a/base/process/launch.h
+++ b/base/process/launch.h
@@ -37,6 +37,24 @@ typedef std::vector<std::pair<int, int> > FileHandleMappingVector;
 // Options for launching a subprocess that are passed to LaunchProcess().
 // The default constructor constructs the object with default options.
 struct BASE_EXPORT LaunchOptions {
+#if defined(OS_POSIX)
+  // Delegate to be run in between fork and exec in the subprocess (see
+  // pre_exec_delegate below)
+  class BASE_EXPORT PreExecDelegate {
+   public:
+    PreExecDelegate() {}
+    virtual ~PreExecDelegate() {}
+
+    // Since this is to be run between fork and exec, and fork may have happened
+    // while multiple threads were running, this function needs to be async
+    // safe.
+    virtual void RunAsyncSafe() = 0;
+
+   private:
+    DISALLOW_COPY_AND_ASSIGN(PreExecDelegate);
+  };
+#endif  // defined(OS_POSIX)
+
   LaunchOptions();
   ~LaunchOptions();
 
@@ -115,6 +133,9 @@ struct BASE_EXPORT LaunchOptions {
 
 #if defined(OS_LINUX)
   // If non-zero, start the process using clone(), using flags as provided.
+  // Unlike in clone, clone_flags may not contain a custom termination signal
+  // that is sent to the parent when the child dies. The termination signal will
+  // always be set to SIGCHLD.
   int clone_flags;
 
   // By default, child processes will have the PR_SET_NO_NEW_PRIVS bit set. If
@@ -122,6 +143,16 @@ struct BASE_EXPORT LaunchOptions {
   bool allow_new_privs;
 #endif  // defined(OS_LINUX)
 
+#if defined(OS_POSIX)
+  // If non-null, a delegate to be run immediately prior to executing the new
+  // program in the child process.
+  //
+  // WARNING: If LaunchProcess is called in the presence of multiple threads,
+  // code running in this delegate essentially needs to be async-signal safe
+  // (see man 7 signal for a list of allowed functions).
+  PreExecDelegate* pre_exec_delegate;
+#endif  // defined(OS_POSIX)
+
 #if defined(OS_CHROMEOS)
   // If non-negative, the specified file descriptor will be set as the launched
   // process' controlling terminal.
@@ -156,12 +187,6 @@ struct BASE_EXPORT LaunchOptions {
 BASE_EXPORT Process LaunchProcess(const CommandLine& cmdline,
                                   const LaunchOptions& options);
 
-// Deprecated version.
-// TODO(rvargas) crbug.com/417532: Remove this after migrating all consumers.
-BASE_EXPORT bool LaunchProcess(const CommandLine& cmdline,
-                               const LaunchOptions& options,
-                               ProcessHandle* process_handle);
-
 #if defined(OS_WIN)
 // Windows-specific LaunchProcess that takes the command line as a
 // string.  Useful for situations where you need to control the
@@ -192,12 +217,6 @@ BASE_EXPORT Process LaunchElevatedProcess(const CommandLine& cmdline,
 BASE_EXPORT Process LaunchProcess(const std::vector<std::string>& argv,
                                   const LaunchOptions& options);
 
-// Deprecated version.
-// TODO(rvargas) crbug.com/417532: Remove this after migrating all consumers.
-BASE_EXPORT bool LaunchProcess(const std::vector<std::string>& argv,
-                               const LaunchOptions& options,
-                               ProcessHandle* process_handle);
-
 // Close all file descriptors, except those which are a destination in the
 // given multimap. Only call this function in a child process where you know
 // that there aren't any other threads.