Set magic string in registry to enable fallback to full installer in case of 3 stage updates.

chrome/installer/mini_installer/mini_installer.h

 // Copyright (c) 2006-2009 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_INSTALLER_MINI_INSTALLER_
 #define CHROME_INSTALLER_MINI_INSTALLER_
 
 // The windows command line to uncompress a LZ compressed file. It is a define
 // because we need the string to be writable. We don't need the full path
 // since it is located in windows\system32 and is available since windows2k.
 #define UNCOMPRESS_CMD L"expand.exe "
 
 namespace mini_installer {
 
 // Various filenames
 const wchar_t kSetupName[] = L"setup.exe";
 const wchar_t kChromePrefix[] = L"chrome";
 const wchar_t kSetupPrefix[] = L"setup";
 
 // setup.exe command line arguements
 const wchar_t kCmdInstallArchive[] = L" --install-archive";
 const wchar_t kCmdUpdateSetupExe[] = L" --update-setup-exe";
 const wchar_t kCmdNewSetupExe[] = L" --new-setup-exe";
 
 // Temp directory prefix that this process creates
 const wchar_t kTempPrefix[] = L"CR_";
+// Google Update will use full installer if this suffix is found in ap key.
+const wchar_t kFullInstallerSuffix[] = L"-full";
 
 // The resource types that would be unpacked from the mini installer.
 // 'BN' is uncompressed binary and 'BL' is LZ compressed binary.
 const wchar_t kBinResourceType[] = L"BN";
 const wchar_t kLZCResourceType[] = L"BL";
 const wchar_t kLZMAResourceType[] = L"B7";
 
 // Registry key to get uninstall command
-const wchar_t kUninstallRegistryValueName[] = L"UninstallString";
+const wchar_t kApRegistryValueName[] = L"ap";
 // Registry key that tells Chrome installer not to delete extracted files.
 const wchar_t kCleanupRegistryValueName[] = L"ChromeInstallerCleanup";
-// Paths for the above two registry keys
+// Registry key to get uninstall command
+const wchar_t kUninstallRegistryValueName[] = L"UninstallString";
+
+// Paths for the above registry keys
 #if defined(GOOGLE_CHROME_BUILD)
+const wchar_t kApRegistryKey[] = L"Software\\Google\\Update\\ClientState\\"
+                                 L"{8A69D345-D564-463c-AFF1-A69D9E530F96}";
 const wchar_t kUninstallRegistryKey[] =
     L"Software\\Microsoft\\Windows\\CurrentVersion\\Uninstall\\Google Chrome";
 const wchar_t kCleanupRegistryKey[] = L"Software\\Google";
 #else
+const wchar_t kApRegistryKey[] = L"Software\\Chromium";
 const wchar_t kUninstallRegistryKey[] =
     L"Software\\Microsoft\\Windows\\CurrentVersion\\Uninstall\\Chromium";
 const wchar_t kCleanupRegistryKey[] = L"Software\\Chromium";
 #endif
 
 // One gigabyte is the biggest resource size that it can handle.
 const int kMaxResourceSize = 1024*1024*1024;
 
 // This is the file that contains the list of files to be linked in the
 // executable. This file is updated by the installer generator tool chain.
 const wchar_t kManifestFilename[] = L"packed_files.txt";
 
 }  // namespace mini_installer
 
 #endif  // CHROME_INSTALLER_MINI_INSTALLER_