Add a "native_support" service.

mojo/services/native_support/public/interfaces/process.mojom

+// 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.
+
+[DartPackage="mojo_services"]
+module native_support;
+
+import "files/public/interfaces/file.mojom";
+import "files/public/interfaces/types.mojom";
+
+// Interface for dealing with (e.g., starting) "native" processes.
+interface Process {
+  // Spawns a process, optionally redirecting stdin/stdout/stderr from/to the
+  // corresponding |mojo.files.File| (if null, redirects from/to /dev/null).
+  // |path| is the path to the binary to execute; |argv| is the argv to give to
+  // the process (if null, it just takes |argv[0]| to be |path| with no other
+  // arguments); |envp| is the environment to give to the process, consisting of
+  // an array of strings of the form "NAME=value" (if null, simply inherits the
+  // environment from the parent, whatever that is).
+  // TODO(vtl): This should really take an array of |mojo.files.File|s (or maybe
+  // two, one for input and the other for output), corresponding to FDs, but the
+  // C++ bindings generator doesn't support arrays of interfaces yet
+  // (https://github.com/domokit/mojo/issues/412).
+  // TODO(vtl): The implementation currently ignores |argv[0]| and always fills
+  // it in with |path|.
+  // TODO(vtl): Inheriting |envp| from the parent is somewhat dubious, and
+  // there's also no way to just specify modifications or limit inheritance.
+  Spawn(string path,
+        array<string>? argv,
+        array<string>? envp,
+        mojo.files.File? stdin_file,
+        mojo.files.File? stdout_file,
+        mojo.files.File? stderr_file,
+        ProcessController& process_controller) => (mojo.files.Error error);
+  // Like |Spawn()|, except that the child's stdin/stdout/stderr are redirected
+  // from/to |terminal_file|, which should be a |mojo.files.File| for a terminal
+  // (i.e., one that behaves like one, including responding to the required
+  // ioctls).
+  SpawnWithTerminal(
+      string path,
+      array<string>? argv,
+      array<string>? envp,
+      mojo.files.File terminal_file,
+      ProcessController& process_controller) => (mojo.files.Error error);
+};
+
+// Interface for controlling a process started by one of |Process|'s facilities
+// (in particular, |Spawn()| or |SpawnWithTerminal()|).
+// TODO(vtl): What does it do if this is closed (without being detached)? Kill
+// with SIGHUP?
+interface ProcessController {
+  // Wait for process completion.
+  // TODO(vtl): Add options (e.g., timeout)?
+  Wait() => (mojo.files.Error error, int32 exit_status);
+
+  // Kill the process with the given signal (note: does not wait). |signal|
+  // should be nonnegative. This is not valid after a successful call to
+  // |Wait()|.
+  // TODO(vtl): Add constants for signals. (For standard POSIX signals, the
+  // values should be the same as the POSIX-specified values, so using POSIX
+  // macros for the values should always be OK.)
+  Kill(int32 signal) => (mojo.files.Error error);
+
+  // TODO(vtl): Add a "Detach()"?
+};