GCAPI should append to the existing experiment_labels instead of clobbering them.

chrome/installer/util/google_update_constants.cc

 // 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/installer/util/google_update_constants.h"
 
 namespace google_update {
 
 const wchar_t kChromeUpgradeCode[] = L"{8A69D345-D564-463C-AFF1-A69D9E530F96}";
 
 const wchar_t kExperimentLabels[] = L"experiment_labels";
+const wchar_t kExperimentLabelSep[] = L";";
 
 const wchar_t kGoogleUpdateUpgradeCode[] =
     L"{430FD4D0-B729-4F61-AA34-91526481799D}";
 
 const wchar_t kGoogleUpdateSetupExe[] = L"GoogleUpdateSetup.exe";
 
 const wchar_t kRegPathClients[] = L"Software\\Google\\Update\\Clients";
 const wchar_t kRegPathClientState[] = L"Software\\Google\\Update\\ClientState";
 const wchar_t kRegPathClientStateMedium[] =
     L"Software\\Google\\Update\\ClientStateMedium";
@@ skipping 35 matching lines @@
 const wchar_t kRegReferralField[] = L"referral";
 const wchar_t kRegRenameCmdField[] = L"cmd";
 const wchar_t kRegRunAsUserField[] = L"RunAsUser";
 const wchar_t kRegSendsPingsField[] = L"SendsPings";
 const wchar_t kRegUninstallCmdLine[] = L"UninstallCmdLine";
 const wchar_t kRegUsageStatsField[] = L"usagestats";
 const wchar_t kRegVersionField[] = L"pv";
 const wchar_t kRegWebAccessibleField[] = L"WebAccessible";
 
 }  // namespace google_update