Extract locking behaviour from ProcessSingleton.

chrome/browser/chrome_process_singleton.h

Index: chrome/browser/chrome_process_singleton.h
diff --git a/chrome/browser/chrome_process_singleton.h b/chrome/browser/chrome_process_singleton.h
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+// 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_CHROME_PROCESS_SINGLETON_H_
+#define CHROME_BROWSER_CHROME_PROCESS_SINGLETON_H_
+
+#include "base/basictypes.h"
+#include "base/files/file_path.h"
+#include "chrome/browser/process_singleton.h"
+#include "chrome/browser/process_singleton_modal_dialog_lock.h"
+#include "chrome/browser/process_singleton_startup_lock.h"
+#include "ui/gfx/native_widget_types.h"
+
+// Composes a basic ProcessSingleton with ProcessSingletonStartupLock and
+// ProcessSingletonModalDialogLock.
+//
+// Notifications from ProcessSingleton will be discarded if a modal dialog is
+// active. Otherwise, until |Unlock()| is called, they will be queued up.
+// Once unlocked, notifications will be passed to the client-supplied
+// NotificationCallback.
+//
+// The client must ensure that SetActiveModalDialog is called appropriately when
+// dialogs are displayed or dismissed during startup. While a dialog is active:
+// 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).
+class ChromeProcessSingleton {
+ public:
+  ChromeProcessSingleton(
+      const base::FilePath& user_data_dir,
+      const ProcessSingleton::NotificationCallback& notification_callback);
+
+  ChromeProcessSingleton(
+      const base::FilePath& user_data_dir,
+      const ProcessSingleton::NotificationCallback& notification_callback,
+      const ProcessSingletonModalDialogLock::SetForegroundWindowHandler&
+          set_foreground_window_handler);
+
+  ~ChromeProcessSingleton();
+
+  // Notify another process, if available. Otherwise sets ourselves as the
+  // singleton instance. Returns PROCESS_NONE if we became the singleton
+  // instance. Callers are guaranteed to either have notified an existing
+  // process or have grabbed the singleton (unless the profile is locked by an
+  // unreachable process).
+  ProcessSingleton::NotifyResult NotifyOtherProcessOrCreate();
+
+  // Clear any lock state during shutdown.
+  void Cleanup();
+
+  // Receives a handle to the active modal dialog, or NULL if the active dialog
+  // is dismissed.
+  void SetActiveModalDialog(gfx::NativeWindow active_dialog);
+
+  // Executes previously queued command-line invocations and allows future
+  // invocations to be executed immediately.
+  void Unlock();

[Nico, 2013/04/18 18:12:13]

"// This only has an effect the first time it's called."

+
+ private:
+  // We compose these two locks with the client-supplied notification callback.
+  // First |modal_dialog_lock_| will discard any notifications that arrive while
+  // a modal dialog is active. Otherwise, it will pass the notification to
+  // |startup_lock_|, which will queue notifications until |Unlock()| is called.
+  // Notifications passing through both locks are finally delivered to our
+  // client.
+  ProcessSingletonStartupLock startup_lock_;
+  ProcessSingletonModalDialogLock modal_dialog_lock_;
+
+  // The basic ProcessSingleton
+  ProcessSingleton process_singleton_;
+
+  DISALLOW_COPY_AND_ASSIGN(ChromeProcessSingleton);
+};
+
+#endif  // CHROME_BROWSER_CHROME_PROCESS_SINGLETON_H_