Support rollback with installerdata in mini_installer

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 1486 matching lines @@
       GetMaxVersionFromArchiveDir(src_path));
   if (!installer_version.get()) {
     LOG(ERROR) << "Did not find any valid version in installer.";
     install_status = INVALID_ARCHIVE;
     installer_state.WriteInstallerResult(install_status,
         IDS_INSTALL_INVALID_ARCHIVE_BASE, NULL);
   } else {
     VLOG(1) << "version to install: " << installer_version->GetString();
     bool proceed_with_installation = true;
 
-    uint32_t higher_products = 0;
-    static_assert(sizeof(higher_products) * 8 > BrowserDistribution::NUM_TYPES,
-                  "too many distribution types");
-    const Products& products = installer_state.products();
-    for (Products::const_iterator it = products.begin(); it < products.end();
-         ++it) {
-      const Product& product = **it;
-      const ProductState* product_state =
-          original_state.GetProductState(system_install,
-                                         product.distribution()->GetType());
-      if (product_state != NULL &&
-          (product_state->version().CompareTo(*installer_version) > 0)) {
-        LOG(ERROR) << "Higher version of "
-                   << product.distribution()->GetDisplayName()
-                   << " is already installed.";
-        higher_products |= (1 << product.distribution()->GetType());
+    if (!IsDowngradeAllowed(prefs)) {
+      uint32_t higher_products = 0;
+      static_assert(
+          sizeof(higher_products) * 8 > BrowserDistribution::NUM_TYPES,
+          "too many distribution types");
+      const Products& products = installer_state.products();
+      for (Products::const_iterator it = products.begin(); it < products.end();
+           ++it) {
+        const Product& product = **it;
+        const ProductState* product_state = original_state.GetProductState(
+            system_install, product.distribution()->GetType());
+        if (product_state != NULL &&
+            (product_state->version().CompareTo(*installer_version) > 0)) {
+          LOG(ERROR) << "Higher version of "
+                     << product.distribution()->GetDisplayName()
+                     << " is already installed.";
+          higher_products |= (1 << product.distribution()->GetType());
+        }
+      }
+
+      if (higher_products != 0) {
+        static_assert(BrowserDistribution::NUM_TYPES == 3,
+                      "add support for new products here");
+        int message_id = IDS_INSTALL_HIGHER_VERSION_BASE;
+        proceed_with_installation = false;
+        install_status = HIGHER_VERSION_EXISTS;
+        installer_state.WriteInstallerResult(install_status, message_id, NULL);
       }
     }
 
-    if (higher_products != 0) {
-      static_assert(BrowserDistribution::NUM_TYPES == 3,
-                    "add support for new products here");
-      int message_id = IDS_INSTALL_HIGHER_VERSION_BASE;
-      proceed_with_installation = false;
-      install_status = HIGHER_VERSION_EXISTS;
-      installer_state.WriteInstallerResult(install_status, message_id, NULL);
-    }
-
     if (proceed_with_installation) {
       base::FilePath prefs_source_path(cmd_line.GetSwitchValueNative(
           switches::kInstallerData));
       install_status = InstallOrUpdateProduct(
           original_state, installer_state, setup_exe, uncompressed_archive,
           temp_path.path(), src_path, prefs_source_path, prefs,
           *installer_version);
 
       int install_msg_base = IDS_INSTALL_FAILED_BASE;
       base::FilePath chrome_exe;
@@ skipping 303 matching lines @@
     // to pass through, since this is only returned on uninstall which is
     // never invoked directly by Google Update.
     return_code = InstallUtil::GetInstallReturnCode(install_status);
   }
 
   installer::EndPersistentHistogramStorage(installer_state.target_path());
   VLOG(1) << "Installation complete, returning: " << return_code;
 
   return return_code;
 }