Reset user data directory and disk cache directory after downgrade.

chrome/installer/setup/install.cc

Index: chrome/installer/setup/install.cc
diff --git a/chrome/installer/setup/install.cc b/chrome/installer/setup/install.cc
index af9662322892c2eaff4361005cd3f522f3cc7383..1251fa6900c22e1cea2cf31be140ce4084091f14 100644
--- a/chrome/installer/setup/install.cc
+++ b/chrome/installer/setup/install.cc
@@ -19,6 +19,7 @@
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
+#include "base/win/registry.h"
 #include "base/win/shortcut.h"
 #include "base/win/windows_version.h"
 #include "chrome/common/chrome_constants.h"
@@ -287,6 +288,29 @@ base::FilePath TruncatePath(const base::FilePath& file_path,
   return truncated_file_path;
 }
 
+base::string16 GetDowngradeVersionPath() {
+  return base::string16(L"Software\\Google\\Update\\ClientState\\") +

[grt (UTC plus 2), 2016/05/19 03:24:18]

use BrowserDistribution::GetStateKey() for this rather than computing it

[zmin, 2016/05/19 23:08:03]

Done. Also changed in user_profiles_cleanup.cc

+         base::string16(google_update::kChromeUpgradeCode);
+}
+
+void AddDowngradeVersion(HKEY root, const base::Version* existing_version) {

[grt (UTC plus 2), 2016/05/19 03:24:18]

is it possible to do this work somewhere in AddInstallWorkItems via WorkItems
(maybe Conditional work items) so that rollback will bring them back to their
previous values in case of error?

+  DCHECK(existing_version);
+  base::win::RegKey key(root, GetDowngradeVersionPath().c_str(),
+                        KEY_QUERY_VALUE | KEY_SET_VALUE);
+  if (!key.HasValue(google_update::kRegDowngradeVersion))
+    key.WriteValue(google_update::kRegDowngradeVersion,
+                   base::ASCIIToUTF16(existing_version->GetString()).c_str());
+}
+
+void RemoveDowngradeVersion(HKEY root, const base::Version& new_version) {
+  base::win::RegKey key(root, GetDowngradeVersionPath().c_str(),
+                        KEY_QUERY_VALUE | KEY_SET_VALUE);
+  base::string16 downgrade_version;
+  if (key.ReadValue(google_update::kRegDowngradeVersion, &downgrade_version) ==
+          ERROR_SUCCESS &&
+      base::Version(base::UTF16ToASCII(downgrade_version)) <= new_version)
+    key.DeleteValue(google_update::kRegDowngradeVersion);
+}

[grt (UTC plus 2), 2016/05/19 03:24:18]

nit: blank line after this

[zmin, 2016/05/19 23:08:03]

Done.

 }  // namespace
 
 namespace installer {
@@ -665,6 +689,11 @@ InstallStatus InstallOrUpdateProduct(
                       &force_chrome_default_for_user);
       }
 
+      if (result == OLD_VERSION_DOWNGRADE || result == IN_USE_DOWNGRADE)
+        AddDowngradeVersion(installer_state.root_key(), existing_version.get());
+      else if (result == NEW_VERSION_UPDATED || result == IN_USE_UPDATED)
+        RemoveDowngradeVersion(installer_state.root_key(), new_version);
+
       RegisterChromeOnMachine(installer_state, *chrome_product,
           make_chrome_default || force_chrome_default_for_user);