Add a self-destruct mechanism to user-level Chrome Frame when it detects that system-level Chrome Frame is present. This is a first step to handling user-to-system-level handoff.

It will cause a user-level install to be correctly replaced with a system-level one once the user logs out and back in again. Additional changelists
will follow that:

1) Ensure full clean-up of the user-level installation.
2) Handle notifications such that logging out and in again isn't required.

BUG=82816
TEST=Install user-level Chrome Frame. 
Review URL: http://codereview.chromium.org/7065024

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@87033 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 36 insertions, 0 deletions

diff --git a/chrome_frame/registry_watcher.h b/chrome_frame/registry_watcher.h
new file mode 100644
index 0000000..bb72e82
--- /dev/null
+++ b/chrome_frame/registry_watcher.h
@@ -0,0 +1,36 @@
+// Copyright (c) 2011 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.
+//
+// A utility class that makes it easy to register for registry change
+// notifications.
+//
+
+#ifndef CHROME_FRAME_REGISTRY_WATCHER_H_
+#define CHROME_FRAME_REGISTRY_WATCHER_H_
+
+#include <windows.h>
+
+class RegistryWatcher {
+ public:
+  typedef void (*NotifyFunc)();
+  RegistryWatcher(HKEY hive, const wchar_t* path, NotifyFunc callback);
+  ~RegistryWatcher();
+
+  bool StartWatching();
+  void StopWatching();
+
+ private:
+  static void CALLBACK WaitCallback(void* param, BOOLEAN wait_fired);
+
+  HKEY registry_key_;
+
+  HANDLE wait_event_;
+  HANDLE wait_handle_;
+  bool stopping_;
+
+  NotifyFunc callback_;
+};
+
+
+#endif  // CHROME_FRAME_REGISTRY_WATCHER_H_