Reset user data directory and disk cache directory after downgrade.

chrome/app/chrome_main_delegate.cc

Index: chrome/app/chrome_main_delegate.cc
diff --git a/chrome/app/chrome_main_delegate.cc b/chrome/app/chrome_main_delegate.cc
index 8ea00c77069be45358207274c58e24df948f0198..514e0ff1fb20f30ba8062e353eb15de9060c0056 100644
--- a/chrome/app/chrome_main_delegate.cc
+++ b/chrome/app/chrome_main_delegate.cc
@@ -60,6 +60,7 @@
 #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"
@@ -719,8 +720,15 @@ void ChromeMainDelegate::PreSandboxStartup() {
 #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?