Introduce the ability to wait for the watcher process to initialize.

components/browser_watcher/watcher_client_win.h

 // Copyright (c) 2014 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 COMPONENTS_BROWSER_WATCHER_WATCHER_CLIENT_WIN_H_
 #define COMPONENTS_BROWSER_WATCHER_WATCHER_CLIENT_WIN_H_
 
 #include "base/callback.h"
 #include "base/macros.h"
 #include "base/process/process.h"
@@ skipping 14 matching lines @@
 
   // Constructs a watcher client that launches its watcher process using the
   // command line generated by |command_line_generator|.
   explicit WatcherClient(const CommandLineGenerator& command_line_generator);
 
   // Launches the watcher process such that the child process is able to inherit
   // a handle to the current process. If use_legacy_launch() is true, this uses
   // a non-threadsafe legacy launch mode that's compatible with Windows XP.
   void LaunchWatcher();
 
+  // Ensures that |handle| may be inherited by the watcher process. |handle|
+  // must still be inheritable, and it's the client's responsibility to
+  // communicate the value of |handle| to the launched process.
+  void AddInheritedHandle(HANDLE handle);
+
+  // Returns the launched process.
+  const base::Process& process() const { return process_; }
+
   // Accessors, exposed only for testing.
   bool use_legacy_launch() const { return use_legacy_launch_; }
   void set_use_legacy_launch(bool use_legacy_launch) {
       use_legacy_launch_ = use_legacy_launch;
   }
-  base::ProcessHandle process() const { return process_.Handle(); }
 
  private:
   // If true, the watcher process will be launched with XP legacy handle
   // inheritance. This is not thread safe and can leak random handles into the
   // child process, but it's the best we can do on XP.
   bool use_legacy_launch_;
 
   // The CommandLineGenerator passed to the constructor.
   CommandLineGenerator command_line_generator_;
 
   // A handle to the launched watcher process. Valid after a successful
   // LaunchWatcher() call.
   base::Process process_;
 
+  std::vector<HANDLE> inherited_handles_;
+
   DISALLOW_COPY_AND_ASSIGN(WatcherClient);
 };
 
 }  // namespace browser_watcher
 
 #endif  // COMPONENTS_BROWSER_WATCHER_WATCHER_CLIENT_WIN_H_