Reset user data directory and disk cache directory after downgrade.

chrome/browser/downgrade/user_data_downgrade.cc

+// Copyright 2016 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/browser/downgrade/user_data_downgrade.h"
+
+#include <string>
+
+#include "base/bind.h"
+#include "base/command_line.h"
+#include "base/files/file_enumerator.h"
+#include "base/files/file_path.h"
+#include "base/files/file_util.h"
+#include "base/path_service.h"
+#include "base/strings/string_util.h"
+#include "base/strings/stringprintf.h"
+#include "base/strings/utf_string_conversions.h"
+#include "base/time/time.h"
+#include "base/version.h"
+#include "base/win/registry.h"
+#include "chrome/browser/policy/policy_path_parser.h"
+#include "chrome/common/chrome_constants.h"
+#include "chrome/common/chrome_paths.h"
+#include "chrome/common/chrome_switches.h"
+#include "chrome/common/chrome_version.h"
+#include "chrome/installer/util/google_update_constants.h"
+#include "chrome/installer/util/install_util.h"
+#include "content/public/browser/browser_thread.h"
+
+namespace {
+
+bool g_is_browser_test = false;
+
+// Return the disk cache dir override value if exists or empty path for default
+// disk cache dir.
+base::FilePath GetDiskCacheDir() {
+  base::FilePath disk_cache_dir;
+  policy::path_parser::CheckDiskCacheDirPolicy(&disk_cache_dir);
+  if (disk_cache_dir.empty()) {
+    base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();
+    disk_cache_dir = command_line->GetSwitchValuePath(switches::kDiskCacheDir);
+  }
+  if (disk_cache_dir.ReferencesParent())
+    return base::MakeAbsoluteFilePath(disk_cache_dir);
+  return disk_cache_dir;
+}
+
+base::FilePath GetLastVersionFile(const base::FilePath& user_data_dir) {
+  return user_data_dir.Append(kDowngradeLastVersionFile);
+}
+
+// Return the temporary path that |source_path| will be renamed to later.
+base::FilePath GetTempDirNameForDelete(const base::FilePath& source_path) {
+  if (source_path.empty())
+    return base::FilePath();
+
+  base::FilePath target_path(source_path.AddExtension(kDowngradeDeleteSuffix));
+  int uniquifier =
+      base::GetUniquePathNumber(source_path, kDowngradeDeleteSuffix);
+  if (uniquifier < 0)
+    return base::FilePath();
+  if (uniquifier > 0) {
+    return target_path.InsertBeforeExtensionASCII(
+        base::StringPrintf(" (%d)", uniquifier));
+  }
+
+  return target_path;
+}
+
+// Rename the |source| directory to |target|. Create |source| directory after
+// rename if |recreate| is true.
+void RenameDirectory(const base::FilePath& source,
+                     const base::FilePath& target,
+                     bool recreate) {
+  if (!source.empty() && !target.empty() && base::Move(source, target) &&
+      recreate) {
+    base::CreateDirectory(source);
+  }
+}
+
+void DeleteAllRenamedUserDirectories(const base::FilePath& path) {
+  if (path.empty())
+    return;
+  base::FilePath dir_name = path.DirName();
+  // Does not support root directory
+  if (dir_name == path)
+    return;
+
+  base::FilePath::StringType pattern =
+      path.BaseName().value() + FILE_PATH_LITERAL("*") + kDowngradeDeleteSuffix;
+  base::FileEnumerator enumerator(dir_name, false,
+                                  base::FileEnumerator::DIRECTORIES, pattern);
+  for (base::FilePath dir = enumerator.Next(); !dir.empty();
+       dir = enumerator.Next()) {
+    base::DeleteFile(dir, true);
+  }
+}
+
+void DeleteMovedUserData(const base::FilePath& user_data_dir,
+                         const base::FilePath& disk_cache_dir) {
+  DeleteAllRenamedUserDirectories(user_data_dir);
+  DeleteAllRenamedUserDirectories(disk_cache_dir);
+}
+
+enum InstallLevel { SYSTEM_INSTALL, USER_INSTALL, UNKNOWN };
+
+InstallLevel GetInstallLevel() {
+  base::FilePath cur_chrome_exe;
+  if (!PathService::Get(base::FILE_EXE, &cur_chrome_exe))
+    return UNKNOWN;
+  if (InstallUtil::IsPerUserInstall(cur_chrome_exe))
+    return USER_INSTALL;
+  else
+    return SYSTEM_INSTALL;
+}
+
+}  // namespace
+
+const base::FilePath::CharType kDowngradeLastVersionFile[] =
+    FILE_PATH_LITERAL("Last Version");
+const base::FilePath::CharType kDowngradeDeleteSuffix[] =
+    FILE_PATH_LITERAL(".CHROME_DELETE");
+
+void MoveUserDataForFirstRunAfterDowngrade() {
+  base::FilePath user_data_dir;
+  if (!PathService::Get(chrome::DIR_USER_DATA, &user_data_dir))
+    return;
+  InstallLevel install_level = GetInstallLevel();
+  if (install_level == UNKNOWN)
+    return;
+  base::Version current_version(chrome::kChromeVersion);
+  base::Version downgrade_version = InstallUtil::GetDowngradeVersion(
+      install_level == SYSTEM_INSTALL, BrowserDistribution::GetDistribution());
+  if (downgrade_version.IsValid() && downgrade_version > current_version) {
+    base::FilePath disk_cache_dir(GetDiskCacheDir());
+    // Without the browser process singleton protection, the directory may be
+    // copied multiple times. In order to prevent that from happening, the temp
+    // directory's name will be computed before the Chrome Version file is
+    // read. Because the deletion will be scheduled after the singleton is
+    // acquired, the directory can only be moved twice in the worst case.
+    // Also, doing this after the downgrade version check to reduce performance
+    // cost for the normal launch.
+    base::FilePath temp_disk_cache_dir(GetTempDirNameForDelete(disk_cache_dir));
+    base::FilePath temp_user_data_dir(GetTempDirNameForDelete(user_data_dir));
+    base::Version last_version = GetLastVersion(user_data_dir);
+    if (last_version.IsValid() && last_version > current_version) {
+      // Do not recreate |disk_cache_dir| as it will be initialized later.
+      RenameDirectory(disk_cache_dir, temp_disk_cache_dir, false);
+      RenameDirectory(user_data_dir, temp_user_data_dir, true);
+    }
+  }
+}
+
+void UpdateLastVersion(const base::FilePath& user_data_dir) {
+  base::WriteFile(GetLastVersionFile(user_data_dir), chrome::kChromeVersion,
+                  strlen(chrome::kChromeVersion));
+}
+
+base::Version GetLastVersion(const base::FilePath& user_data_dir) {

[brettw, 2016/06/10 22:42:42]

I really think we need some kind of namespace for this file. Some of these
functions, especially this one, are very generic.

I would be file with just "namespace downgrade" wrapping all files in this
directory.

+  std::string last_version_str;
+  if (base::ReadFileToString(GetLastVersionFile(user_data_dir),
+                             &last_version_str)) {
+    return base::Version(
+        base::TrimWhitespaceASCII(last_version_str, base::TRIM_ALL)
+            .as_string());
+  }
+  return base::Version();
+}
+
+void DeleteMovedUserDataSoon() {
+  base::FilePath user_data_dir;
+  PathService::Get(chrome::DIR_USER_DATA, &user_data_dir);
+  if (g_is_browser_test) {
+    // Delete task will always be posted and executed for browser test.
+    content::BrowserThread::PostBlockingPoolTask(
+        FROM_HERE,
+        base::Bind(&DeleteMovedUserData, user_data_dir, GetDiskCacheDir()));
+  } else {
+    content::BrowserThread::PostAfterStartupTask(
+        FROM_HERE, content::BrowserThread::GetBlockingPool()
+                       ->GetTaskRunnerWithShutdownBehavior(
+                           base::SequencedWorkerPool::CONTINUE_ON_SHUTDOWN),
+        base::Bind(&DeleteMovedUserData, user_data_dir, GetDiskCacheDir()));
+  }
+}
+
+bool IsMSIInstall() {
+  InstallLevel install_level = GetInstallLevel();
+  base::win::RegKey key;
+  DWORD is_msi = 3;
+  return install_level != UNKNOWN &&
+         key.Open((install_level == SYSTEM_INSTALL) ? HKEY_LOCAL_MACHINE
+                                                    : HKEY_CURRENT_USER,
+                  BrowserDistribution::GetDistribution()->GetStateKey().c_str(),
+                  KEY_QUERY_VALUE | KEY_WOW64_32KEY) == ERROR_SUCCESS &&
+         key.ReadValueDW(google_update::kRegMSIField, &is_msi) ==
+             ERROR_SUCCESS &&
+         is_msi != 0;
+}
+
+void SimulateDowngradeForTest(bool is_browser_test) {

[brettw, 2016/06/10 22:42:42]

I was confused about this function since from the name I was expecting calling
it to turn on test mode, and the arg to do something around browser_tests vs.
other tyeps of test.

How about this naming:
  void SetSimulateDowngradeForTest(bool similate_downgrade)

+  g_is_browser_test = is_browser_test;
+}