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

chrome/app/chrome_watcher_command_line_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 CHROME_APP_CHROME_WATCHER_COMMAND_LINE_WIN_H_
 #define CHROME_APP_CHROME_WATCHER_COMMAND_LINE_WIN_H_
 
 #include <windows.h>
 
 #include "base/win/scoped_handle.h"
 
 namespace base {
 class CommandLine;
 class FilePath;
 }  // namespace base
 
 // Generates a CommandLine that will launch |chrome_exe| in Chrome Watcher mode
-// to observe |parent_process|.
+// to observe |parent_process|. The watcher process will signal
+// |on_initialized_event| when its initialization is complete.
 base::CommandLine GenerateChromeWatcherCommandLine(
     const base::FilePath& chrome_exe,
-    HANDLE parent_process);
+    HANDLE parent_process,
+    HANDLE on_initialized_event);
 
 // Interprets the Command Line used to launch a Chrome Watcher process and
-// extracts the parent process HANDLE. Verifies that the handle is usable in
-// this process before returning it, and returns NULL in case of a failure.
-base::win::ScopedHandle InterpretChromeWatcherCommandLine(
-    const base::CommandLine& command_line);
+// extracts the parent process and initialization event HANDLEs. Verifies that
+// the handles are usable in this process before returning them. Returns true if
+// both handles are successfully parsed and false otherwise. If only one of the
+// handles can be parsed, it will be closed.
+bool InterpretChromeWatcherCommandLine(
+    const base::CommandLine& command_line,
+    base::win::ScopedHandle* parent_process,
+    base::win::ScopedHandle* on_initialized_event);
 
 #endif  // CHROME_APP_CHROME_WATCHER_COMMAND_LINE_WIN_H_