Handle upgrade case from previous MSI install.

chrome/installer/setup/setup_main.cc

Index: chrome/installer/setup/setup_main.cc
diff --git a/chrome/installer/setup/setup_main.cc b/chrome/installer/setup/setup_main.cc
index ee2601f50fcf4f65074f4a426bd15201f6a7d62a..08f12921f1bb3f94eaa5aee8a1befe624d3b1803 100644
--- a/chrome/installer/setup/setup_main.cc
+++ b/chrome/installer/setup/setup_main.cc
@@ -1654,14 +1654,33 @@ InstallStatus InstallProductsHelper(const InstallationState& original_state,
   // 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.