If Chrome Binaries version > App Host version, then update App Host.

chrome/browser/extensions/app_host/app_host_upgrade.h

+// Copyright (c) 2012 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_EXTENSIONS_APP_HOST_APP_HOST_UPGRADE_H_
+#define CHROME_BROWSER_EXTENSIONS_APP_HOST_APP_HOST_UPGRADE_H_
+
+class Version;
+
+namespace app_host {
+
+extern const wchar_t kMultiInstallAppGuid[];
+extern const wchar_t kChromeAppHostAppGuid[];
+
+// Fetches the app version ("pv" entry) of a Google product, given the
+// app GUID ("{###...###}") and the installation level.
+// Returns: true if successful.

[erikwright (departed), 2012/09/13 13:48:26]

Remove the ':'. "Returns true if successful."

Also below.

[huangs, 2012/09/13 18:46:00]

Done (2 instances).

+bool GetAppVersionForInstallationLevel(const wchar_t* app_guid,

[grt (UTC plus 2), 2012/09/13 13:14:43]

Version has value semantics (see the log message for r88143). a new convention
is for functions like this to return a Version instance and for the caller to
use its IsValid() method to determine if it got a version or not.  this often
simplifies things since callers no longer need to test two different things (did
the fn return true and is the version it gave valid).

[grt (UTC plus 2), 2012/09/13 13:14:43]

please remove "ForInstallationLevel". it's superfluous and inconsistent with
most/all other function that takes a bool for system_level or user_level.

[huangs, 2012/09/13 18:46:00]

Done (for Version).

[huangs, 2012/09/13 18:46:00]

Done for "ForInstallationLevel", but only limited to the functions that take
bool.

+                                       bool system_level,
+                                       Version* version);
+
+// Calls setup.exe to reinstall App Host, using setup.exe for the

[grt (UTC plus 2), 2012/09/13 13:14:43]

"reinstall" -> "update"

[huangs, 2012/09/13 18:46:00]

Done.

+// specified installation level.
+// Returns: true if successful.
+bool UpgradeAppHost(bool system_level);
+
+}  // namespace app_host
+
+#endif  // CHROME_BROWSER_EXTENSIONS_APP_HOST_APP_HOST_UPGRADE_H_