Extract locking behaviour from ProcessSingleton.

chrome/browser/process_singleton_modal_dialog_lock.h

+// Copyright (c) 2013 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_BROWSER_PROCESS_SINGLETON_MODAL_DIALOG_LOCK_H_
+#define CHROME_BROWSER_PROCESS_SINGLETON_MODAL_DIALOG_LOCK_H_
+
+#include "base/basictypes.h"
+#include "base/callback_forward.h"
+#include "chrome/browser/process_singleton.h"
+#include "ui/gfx/native_widget_types.h"
+
+class CommandLine;
+
+namespace base {
+class FilePath;
+}
+
+// Provides a ProcessSingleton::NotificationCallback that prevents
+// command-line handling when a modal dialog is active during startup. The
+// client must ensure that SetActiveModalDialog is called appropriately when
+// dialogs are displayed or dismissed.

[gab, 2013/04/09 14:34:29]

s/when dialogs/when such dialogs
?
Since it's only for dialogs for which we want this lock to have an impact on?

+//
+// While a dialog is active, the ProcessSingleton notification
+// callback will handle but ignore notifications:
+// 1. Neither this process nor the invoking process will handle the command
+//    line.
+// 2. The active dialog is brought to the foreground and/or the taskbar icon
+//    flashed (using ::SetForegroundWindow on Windows).
+//
+// Otherwise, the notification is forwarded to a wrapped NotificationCallback.
+class ProcessSingletonModalDialogLock {
+ public:
+  typedef base::Callback<void(gfx::NativeWindow)> SetForegroundWindowHandler;
+  explicit ProcessSingletonModalDialogLock(
+      const ProcessSingleton::NotificationCallback& original_callback);
+
+  ProcessSingletonModalDialogLock(
+      const ProcessSingleton::NotificationCallback& original_callback,
+      const SetForegroundWindowHandler& set_foreground_window_handler);
+
+  ~ProcessSingletonModalDialogLock();
+
+  // Receives a handle to the active modal dialog, or NULL if the active dialog
+  // is dismissed.
+  void SetActiveModalDialog(gfx::NativeWindow active_dialog);
+
+  // Returns the ProcessSingleton::NotificationCallback.
+  // The callback is only valid during the lifetime of the
+  // ProcessSingletonModalDialogLock instance.
+  ProcessSingleton::NotificationCallback AsNotificationCallback();
+
+ private:
+  bool NotificationCallbackImpl(const CommandLine& command_line,
+                                const base::FilePath& current_directory);
+
+  gfx::NativeWindow active_dialog_;
+  ProcessSingleton::NotificationCallback original_callback_;
+  SetForegroundWindowHandler set_foreground_window_handler_;
+
+  DISALLOW_COPY_AND_ASSIGN(ProcessSingletonModalDialogLock);
+};
+
+#endif  // CHROME_BROWSER_PROCESS_SINGLETON_MODAL_DIALOG_LOCK_H_