Reset user data directory and disk cache directory after downgrade.

chrome/installer/util/install_util.cc

Index: chrome/installer/util/install_util.cc
diff --git a/chrome/installer/util/install_util.cc b/chrome/installer/util/install_util.cc
index c5568048da4978a6a33234dc036ac5228fa95b7e..4a106c3a806ba9e804beba2c2afcef837d7d1512 100644
--- a/chrome/installer/util/install_util.cc
+++ b/chrome/installer/util/install_util.cc
@@ -44,6 +44,7 @@ using installer::ProductState;
 
 namespace {
 
+const wchar_t kRegDowngradeVersion[] = L"DowngradeVersion";
 const wchar_t kStageBinaryPatching[] = L"binary_patching";
 const wchar_t kStageBuilding[] = L"building";
 const wchar_t kStageConfiguringAutoLaunch[] = L"configuring_auto_launch";
@@ -630,6 +631,47 @@ bool InstallUtil::ProgramCompare::GetInfo(const base::File& file,
   return GetFileInformationByHandle(file.GetPlatformFile(), info) != 0;
 }
 
+// static
+base::Version InstallUtil::GetDowngradeVersion(
+    bool system_install,
+    const BrowserDistribution* dist) {
+  DCHECK(dist);
+  base::win::RegKey key;
+  base::string16 downgrade_version;
+  if (key.Open(system_install ? HKEY_LOCAL_MACHINE : HKEY_CURRENT_USER,
+               dist->GetStateKey().c_str(),
+               KEY_QUERY_VALUE | KEY_WOW64_32KEY) != ERROR_SUCCESS ||
+      key.ReadValue(kRegDowngradeVersion, &downgrade_version) !=
+          ERROR_SUCCESS) {
+    return base::Version();
+  }
+  return base::Version(base::UTF16ToASCII(downgrade_version));
+}
+
+// static
+void InstallUtil::AddUpdateDowngradeVersionItem(
+    bool system_install,
+    const base::Version* current_version,
+    const base::Version& new_version,
+    const BrowserDistribution* dist,
+    WorkItemList* list) {
+  DCHECK(list);
+  DCHECK(dist);
+  DCHECK_EQ(BrowserDistribution::CHROME_BROWSER, dist->GetType());
+  base::Version downgrade_version = GetDowngradeVersion(system_install, dist);
+  HKEY root = system_install ? HKEY_LOCAL_MACHINE : HKEY_CURRENT_USER;
+  if (!current_version ||
+      (*current_version <= new_version &&
+       ((!downgrade_version.IsValid() || downgrade_version <= new_version)))) {
+    list->AddDeleteRegValueWorkItem(root, dist->GetStateKey(), KEY_WOW64_32KEY,
+                                    kRegDowngradeVersion);
+  } else if (*current_version > new_version && !downgrade_version.IsValid()) {
+    list->AddSetRegValueWorkItem(
+        root, dist->GetStateKey(), KEY_WOW64_32KEY, kRegDowngradeVersion,
+        base::ASCIIToUTF16(current_version->GetString()), true);
+  }
+}
+
 InstallUtil::ProgramCompare::ProgramCompare(const base::FilePath& path_to_match)
     : ProgramCompare(path_to_match, ComparisonType::FILE) {}