Handle upgrade case from previous MSI install.

chrome/installer/setup/setup_main.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/setup/setup_main.h"
 
 #include <windows.h>
 #include <msi.h>
 #include <shellapi.h>
 #include <shlobj.h>
@@ skipping 1636 matching lines @@
     for (Products::const_iterator it = products.begin(); it < products.end();
          ++it) {
       const Product& product = **it;
       product.LaunchUserExperiment(setup_path, install_status, system_install);
     }
   }
 
   // If the installation completed successfully...
   if (InstallUtil::GetInstallReturnCode(install_status) == 0) {
     // Update the DisplayVersion created by an MSI-based install.
+    base::FilePath master_preferences_file(
+      installer_state.target_path().AppendASCII(
+          installer::kDefaultMasterPrefs));
     std::string install_id;
     if (prefs.GetString(installer::master_preferences::kMsiProductId,
                         &install_id)) {
+      // A currently active MSI install will have specified the master-
+      // preferences file on the command-line that includes the product-id.
+      // We must delay the setting of the DisplayVersion until after the
+      // grandparent "msiexec" process has exited.
       base::FilePath new_setup =
           installer_state.GetInstallerDirectory(*installer_version)
           .Append(kSetupExe);
       DelayedOverwriteDisplayVersions(
           new_setup, install_id, *installer_version);
+    } else if (base::PathExists(master_preferences_file)) {

[grt (UTC plus 2), 2015/09/25 15:01:27]

I don't think it's safe to rely on the value being in master_preferences. There
is documentation on the internets saying that admins can do what they wish with
this file to control Chrome. These don't say "be sure not to touch the msi
product id". I think it's more reliable to get the value from the
EnterpriseProduct value name in the ClientState key.

[robertshield, 2015/09/25 15:19:20]

I tend to agree, relying on master_preferences to be un-molested seems a little
fragile. I can't think of any reason not to use the value in the ClientState key
off the top of my head and I agree that seems more reliable.

[bcwhite, 2015/10/01 13:11:53]

I'll look into the ClientState key.  Is it okay to do this check first, before
looking there or skip this completely?

[grt (UTC plus 2), 2015/10/01 14:37:58]

My inclination is to only check the one authoritative source of data.
https://codereview.chromium.org/749133003/ has Robert's code for extracting the
product id from ClientState.

+      // In the case of an original MSI install, the master-preferences file
+      // exists but was not passed on the command-line.  We load it explicitly
+      // to get the product-id and then, because there is no "msiexec" process
+      // to out-wait, we set the DisplayVersion immediately.
+      const MasterPreferences mp(master_preferences_file);
+      if (mp.GetString(installer::master_preferences::kMsiProductId,
+                       &install_id)) {
+        OverwriteDisplayVersions(base::UTF8ToUTF16(install_id),
+                                 base::UTF8ToUTF16(
+                                     installer_version->GetString()));
+      }
     }
     // Return the path to the directory containing the newly installed
     // setup.exe and uncompressed archive if the caller requested it.
     if (installer_directory) {
       *installer_directory =
           installer_state.GetInstallerDirectory(*installer_version);
     }
   }
 
   // temp_path's dtor will take care of deleting or scheduling itself for
@@ skipping 151 matching lines @@
     // Note that we allow the status installer::UNINSTALL_REQUIRES_REBOOT
     // to pass through, since this is only returned on uninstall which is
     // never invoked directly by Google Update.
     return_code = InstallUtil::GetInstallReturnCode(install_status);
   }
 
   VLOG(1) << "Installation complete, returning: " << return_code;
 
   return return_code;
 }