Force migrate all clients from multi-install back to single-install.

chrome/installer/mini_installer/chrome_appid.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/mini_installer/appid.h"
 
 namespace google_update {
+
+#if defined(GOOGLE_CHROME_BUILD)
 const wchar_t kAppGuid[] = L"{8A69D345-D564-463c-AFF1-A69D9E530F96}";
 const wchar_t kMultiInstallAppGuid[] =
     L"{4DC8B4CA-1BDA-483e-B5FA-D3C12E15B62D}";
 const wchar_t kSxSAppGuid[] = L"{4ea16ac7-fd5a-47c3-875b-dbf4a2008c20}";
-}
+#else
+const wchar_t kAppGuid[] = L"";

[gab, 2016/12/12 21:38:16]

Chromium has no appguid? Also, if we follow models in the rest of the installer,
this would typically be in a separate file and each file included in the right
build?

[grt (UTC plus 2), 2016/12/13 09:20:37]

No. Chromium doesn't integrate with Google Update, hence no appguid. Chromium
puts all "Clients" and "ClientState" values into the key "...\SOFTWARE\Chromium"
for the browser and "...\SOFTWARE\Chromium Binaries" for the binaries.
That's a world I'm moving to in https://crrev.com/432270 and others to come. I
hope that one day that stuff will be available in the mini_installer. For now,
though, we'll stick with mini_installer being a bit of a hack on its own. :-)

+const wchar_t kMultiInstallAppGuid[] = L"";
+const wchar_t kSxSAppGuid[] = L"";
+#endif
+
+}  // namespace google_update