Reset user data directory and disk cache directory after downgrade.

chrome/app/chrome_main_delegate.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/app/chrome_main_delegate.h"
 
 #include <stddef.h>
 #include <string>
 
 #include "base/base_paths.h"
@@ skipping 42 matching lines @@
 #include "extensions/common/constants.h"
 #include "ui/base/material_design/material_design_controller.h"
 #include "ui/base/resource/resource_bundle.h"
 #include "ui/base/ui_base_switches.h"
 
 #if defined(OS_WIN)
 #include <atlbase.h>
 #include <malloc.h>
 #include <algorithm>
 #include "base/debug/close_handle_hook_win.h"
+#include "chrome/browser/downgrade/user_data_downgrade.h"
 #include "chrome/common/child_process_logging.h"
 #include "chrome/common/v8_breakpad_support_win.h"
 #include "components/crash/content/app/crashpad.h"
 #include "sandbox/win/src/sandbox.h"
 #include "ui/base/resource/resource_bundle_win.h"
 #endif
 
 #if defined(OS_MACOSX)
 #include "base/mac/foundation_util.h"
 #include "chrome/app/chrome_main_mac.h"
@@ skipping 639 matching lines @@
 #if defined(OS_WIN)
   child_process_logging::Init();
 #endif
 #if defined(ARCH_CPU_ARM_FAMILY) && (defined(OS_ANDROID) || defined(OS_LINUX))
   // Create an instance of the CPU class to parse /proc/cpuinfo and cache
   // cpu_brand info.
   base::CPU cpu_info;
 #endif
 
   // Initialize the user data dir for any process type that needs it.
-  if (chrome::ProcessNeedsProfileDir(process_type))
+  if (chrome::ProcessNeedsProfileDir(process_type)) {
     InitializeUserDataDir();
+#if defined(OS_WIN) && !defined(CHROME_MULTIPLE_DLL_CHILD)
+    MoveUserDataForFirstRunAfterDowngrade();

[grt (UTC plus 2), 2016/06/07 01:25:28]

since the first thing Move... does is get DIR_USER_DATA, how about taking it as
an in-param and moving this statement down within the "if" below?

[zmin, 2016/06/07 14:41:49]

MoveUserDataForFirstRunAfterDowngrade() not only moves user data dir but also
disk cache dir.  There is more consistency if both paths are obtained inside the
function. Also it reduces the number parameters of the function. Even though
PathService::Get will be called twice I think it is a better choice. 

[grt (UTC plus 2), 2016/06/07 15:40:43]

That's a good argument. Why does UpdateBrowserVersion take the user data dir as
an in param, then?

+    base::FilePath user_data_dir;
+    if (PathService::Get(chrome::DIR_USER_DATA, &user_data_dir))
+      UpdateBrowserVersion(user_data_dir);
+#endif
+  }
 
   // Register component_updater PathProvider after DIR_USER_DATA overidden by
   // command line flags. Maybe move the chrome PathProvider down here also?
   component_updater::RegisterPathProvider(chrome::DIR_USER_DATA);
 
   // Enable Message Loop related state asap.
   if (command_line.HasSwitch(switches::kMessageLoopHistogrammer))
     base::MessageLoop::EnableHistogrammer(true);
 
 #if !defined(OS_ANDROID) && !defined(OS_WIN)
@@ skipping 285 matching lines @@
     case version_info::Channel::CANARY:
       return true;
     case version_info::Channel::DEV:
     case version_info::Channel::BETA:
     case version_info::Channel::STABLE:
     default:
       // Don't enable instrumentation.
       return false;
   }
 }