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

chrome/browser/extensions/app_host/update.cc

Index: chrome/browser/extensions/app_host/update.cc
diff --git a/chrome/browser/extensions/app_host/update.cc b/chrome/browser/extensions/app_host/update.cc
new file mode 100755
index 0000000000000000000000000000000000000000..274df940ae8e05615aa633e31bdf38a43ccde0a0
--- /dev/null
+++ b/chrome/browser/extensions/app_host/update.cc
@@ -0,0 +1,101 @@
+// 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.
+
+#include "chrome/browser/extensions/app_host/update.h"
+
+#include <windows.h>
+#include "base/command_line.h"
+#include "base/file_version_info.h"
+#include "base/logging.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/process_util.h"
+#include "base/string16.h"
+#include "base/string_util.h"
+#include "base/version.h"
+#include "base/win/registry.h"
+#include "chrome/installer/launcher_support/chrome_launcher_support.h"
+
+namespace app_host {
+
+namespace {
+
+// http://crbug.com/148538
+// TODO(huangs) Refactor the constants:
+const wchar_t kGoogleRegClientsKey[] = L"Software\\Google\\Update\\Clients\\";
+
+// Copied from util_constants.cc.
+const char kMultiInstall[] = "multi-install";
+const char kChromeAppHost[] = "app-host";
+const char kVerboseLogging[] = "verbose-logging";
+
+// Copied from google_update_constants.cc.
+const wchar_t kRegVersionField[] = L"pv";
+
+// Copied from chrome_appid.cc and google_chrome_binaries_distribution.cc.
+const wchar_t kChromeBinariesAppGuid[] =
+    L"{4DC8B4CA-1BDA-483e-B5FA-D3C12E15B62D}";
+const wchar_t kChromeAppGuid[] = L"{8A69D345-D564-463c-AFF1-A69D9E530F96}";
+
+// Fetches the version of the App Host, directly from the process.
+Version GetAppHostVersion() {
+  scoped_ptr<FileVersionInfo> version_info(
+      FileVersionInfo::CreateFileVersionInfoForCurrentModule());
+  return Version(WideToASCII(version_info->product_version()));
+}
+
+// Fetches the app version ("pv" entry) of a Google product from the
+// system-level registry, given the app GUID ("{###...###}").
+Version GetAppVersionFromRegistry(const wchar_t* app_guid) {
+  HKEY root_key = HKEY_LOCAL_MACHINE;
+  string16 client_key(kGoogleRegClientsKey);
+  client_key.append(app_guid);
+  base::win::RegKey reg_key;
+  string16 version_str;
+  if ((reg_key.Open(root_key, client_key.c_str(),
+                    KEY_QUERY_VALUE) == ERROR_SUCCESS) &&
+      (reg_key.ReadValue(kRegVersionField, &version_str) == ERROR_SUCCESS)) {
+    return Version(WideToASCII(version_str));
+  }
+  return Version();
+}
+
+// Calls setup.exe to update App Host, using the system-level setup.exe.
+bool UpdateAppHost() {
+  // Get the path to the setup.exe.
+  FilePath setup_exe(
+      chrome_launcher_support::GetSetupExeForInstallationLevel(
+          chrome_launcher_support::SYSTEM_LEVEL_INSTALLATION));
+  if (setup_exe.empty()) {
+    LOG(ERROR) << "Failed to find setup.exe";
+    return false;
+  }
+  CommandLine cmd_line(setup_exe);
+  cmd_line.AppendSwitch(kMultiInstall);
+  cmd_line.AppendSwitch(kChromeAppHost);
+  cmd_line.AppendSwitch(kVerboseLogging);
+  LOG(INFO) << "Launching: " << cmd_line.GetCommandLineString();
+  return base::LaunchProcess(cmd_line, base::LaunchOptions(), NULL);
+}
+
+}  // namespace
+
+void EnsureAppHostUpToDate() {
+  // Check version from Chrome Binaries first, then Chrome (all system-level).
+  Version new_version;

[erikwright (departed), 2012/09/14 01:21:36]

combine declaration and assignment (lines 85,86)

[huangs, 2012/09/14 04:03:14]

Done.

+  new_version = GetAppVersionFromRegistry(kChromeBinariesAppGuid);
+  if (!new_version.IsValid())
+    new_version = GetAppVersionFromRegistry(kChromeAppGuid);
+  if (!new_version.IsValid())
+    return;  // Not an error: System-level Chrome might not be installed.
+  Version app_host_version(GetAppHostVersion());
+  DCHECK(app_host_version.IsValid());
+  if (app_host_version.IsOlderThan(new_version.GetString())) {
+    LOG(INFO) << "Updating App Host from " << app_host_version.GetString()
+              << " to " << new_version.GetString();
+    if (!UpdateAppHost())

[erikwright (departed), 2012/09/14 01:21:36]

I think this should be renamed to LaunchAppHostUpdate() because it doesn't wait
for the update to complete. Right now it's misleading.

[huangs, 2012/09/14 04:03:14]

Done.

[erikwright (departed), 2012/09/14 13:21:24]

Sorry, misunderstanding:

EnsureAppHostUpToDate was correctly named.
UpdateAppHost should be renamed to LaunchAppHostUpdate

[huangs, 2012/09/14 16:34:23]

Done.

+      LOG(ERROR) << "Failed to update App Host";

[erikwright (departed), 2012/09/14 01:21:36]

"Failed to launch App Host update."

[huangs, 2012/09/14 04:03:14]

Done.

+  }
+}
+
+}  // namespace app_host