Don't accidentally propagate Omaha variable to child processes.

chrome/installer/util/util_constants.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.
 //
 // Defines all install related constants that need to be used by Chrome as
 // well as Chrome Installer.
 
 #ifndef CHROME_INSTALLER_UTIL_UTIL_CONSTANTS_H_
 #define CHROME_INSTALLER_UTIL_UTIL_CONSTANTS_H_
 
@@ skipping 200 matching lines @@
 extern const char kUninstallMetricsName[];
 extern const wchar_t kUninstallStringField[];
 
 // Google Update installer result API
 extern const wchar_t kInstallerError[];
 extern const wchar_t kInstallerExtraCode1[];
 extern const wchar_t kInstallerResult[];
 extern const wchar_t kInstallerResultUIString[];
 extern const wchar_t kInstallerSuccessLaunchCmdLine[];
 
-// Google Update named environment variable that implies kSystemLevel.
-extern const char kGoogleUpdateIsMachineEnvVar[];
-
 // Product options.
 extern const wchar_t kOptionMultiInstall[];
 extern const wchar_t kOptionReadyMode[];
 extern const wchar_t kOptionAppHostIsLauncher[];
 
 // Chrome channel display names.
 // NOTE: Canary is not strictly a 'channel', but rather a separate product
 //     installed side-by-side. However, GoogleUpdateSettings::GetChromeChannel
 //     will return "canary" for that product.
 extern const wchar_t kChromeChannelUnknown[];
 extern const wchar_t kChromeChannelCanary[];
 extern const wchar_t kChromeChannelDev[];
 extern const wchar_t kChromeChannelBeta[];
 extern const wchar_t kChromeChannelStable[];
 
 extern const size_t kMaxAppModelIdLength;
 
 }  // namespace installer
 
 #endif  // CHROME_INSTALLER_UTIL_UTIL_CONSTANTS_H_