Browser watcher first installment.

components/browser_watcher/watcher_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_WIN_H_
+#define COMPONENTS_BROWSER_WATCHER_WATCHER_WIN_H_
+
+#include "base/macros.h"
+#include "base/process/process_handle.h"
+#include "base/strings/string16.h"
+#include "base/time/time.h"
+#include "base/win/scoped_handle.h"
+
+namespace base {
+class CommandLine;
+}
+
+namespace browser_watcher {
+
+// Watches for the exit code of a process and records it in a given registry
+// location.
+class ExitCodeWatcher {
+ public:
+  // Initialize the watcher with a registry path.
+  explicit ExitCodeWatcher(const base::char16* registry_path);
+  ~ExitCodeWatcher();
+
+  // Initializes from arguments on |cmd_line|, returns true on success.
+  // This function expects the process handle indicated in |cmd_line| to be open
+  // with sufficient privilege to wait and retrieve the process exit code.
+  // It checks the handle for validity and takes ownership of it.
+  // The intent is for this handle to be inherited into the watcher process
+  // hosting the instance of this class.

[erikwright (departed), 2014/11/17 18:12:30]

Once you have exposed the flag as a public static constant update this comment
to refer to it.

Alternatively, create a symmetrical pair of free functions to parse and generate
the command lines that can be used in the client and server, and update this
class to take a HANDLE rather than parsing it out itself.

As things currently stand, this class cannot be used/tested without digging into
its implementation and duplicating a constant hidden there, which is
problematic.

[Sigurður Ásgeirsson, 2014/11/17 21:27:12]

Done.

+  bool ParseArguments(const base::CommandLine& cmd_line);
+
+  // Waits for the process to exit and records its exit code in registry.
+  // This is a blocking call.
+  void WaitForExit();
+
+  base::ProcessHandle process() const { return process_.Get(); }
+
+ private:
+  // The registry path the exit codes are written to.
+  base::string16 registry_path_;
+
+  // Handle, PID, and creation time of the watched process.
+  base::win::ScopedHandle process_;
+  base::ProcessId process_pid_;
+  base::Time process_creation_time_;
+
+  DISALLOW_COPY_AND_ASSIGN(ExitCodeWatcher);
+};
+
+}  // namespace browser_watcher
+
+#endif  // COMPONENTS_BROWSER_WATCHER_WATCHER_WIN_H_