Revamp the MigrateBrowserPrefs and MigrateUserPrefs code.

chrome/browser/ui/browser_window_state.cc

Index: chrome/browser/ui/browser_window_state.cc
diff --git a/chrome/browser/ui/browser_window_state.cc b/chrome/browser/ui/browser_window_state.cc
index f31e5ec984c1118306875d5c941d6f55af601ad7..dc224d10cab05c1589501ae8c589cb8485f9497f 100644
--- a/chrome/browser/ui/browser_window_state.cc
+++ b/chrome/browser/ui/browser_window_state.cc
@@ -70,8 +70,7 @@ class WindowPlacementPrefUpdate : public DictionaryPrefUpdate {
 
 std::string GetWindowName(const Browser* browser) {
   if (browser->app_name().empty()) {
-    return browser->is_type_popup() ?
-        prefs::kBrowserWindowPlacementPopup : prefs::kBrowserWindowPlacement;

[gab, 2015/02/23 16:09:38]

Do not change this code.

The migration code you removed moved the pref from Local State (browser prefs)
to per-profile state (user prefs), it doesn't get rid of the pref per se.

[rkaplow, 2015/02/23 23:27:52]

Done.

+    return prefs::kBrowserWindowPlacementPopup;
   }
   return browser->app_name();
 }