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

components/browser_watcher/watcher_client_win.cc

 // 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.
 
 #include "components/browser_watcher/watcher_client_win.h"
 
 #include <windows.h>
 
 #include "base/command_line.h"
 #include "base/logging.h"
@@ skipping 30 matching lines @@
   base::HandlesToInheritVector to_inherit;
   base::LaunchOptions options;
   options.start_hidden = true;
   if (use_legacy_launch_) {
     // Launch the child process inheriting all handles on XP.
     options.inherit_handles = true;
   } else {
     // Launch the child process inheriting only |self| on
     // Vista and better.
     to_inherit.push_back(self.Handle());
+    to_inherit.insert(to_inherit.end(), inherited_handles_.begin(),
+                      inherited_handles_.end());
     options.handles_to_inherit = &to_inherit;
   }
 
   process_ = base::LaunchProcess(cmd_line, options);
   if (!process_.IsValid())
     LOG(ERROR) << "Failed to launch browser watcher.";
 }
 
+void WatcherClient::AddInheritedHandle(HANDLE handle) {
+  inherited_handles_.push_back(handle);
+}
+
 }  // namespace browser_watcher