Reland - cros: Add CHECK for screen unlock problem

chrome/browser/chromeos/login/screen_locker.cc

Index: chrome/browser/chromeos/login/screen_locker.cc
diff --git a/chrome/browser/chromeos/login/screen_locker.cc b/chrome/browser/chromeos/login/screen_locker.cc
index 068240403bd894a0b215198bbe35391e84186e19..a3a369bbb497189724bc6fcb0d2bcfac7313f952 100644
--- a/chrome/browser/chromeos/login/screen_locker.cc
+++ b/chrome/browser/chromeos/login/screen_locker.cc
@@ -323,8 +323,14 @@ void ScreenLocker::InitClass() {
 ScreenLocker::~ScreenLocker() {
   DCHECK(MessageLoop::current()->type() == MessageLoop::TYPE_UI);
   ClearErrors();
-  ash::Shell::GetInstance()->
+  bool moved = ash::Shell::GetInstance()->
       desktop_background_controller()->MoveDesktopToUnlockedContainer();
+  // If we didn't reparent the desktop background then the screen would be
+  // unlocked but the user's windows are hidden, making the UI unusable.
+  // Similar symptoms are happening in the field. Check if this is the cause.
+  // See crbug.com/149043
+  CHECK(moved);
+  LOG(WARNING) << "JAMESDEBUG screen locked moved " << moved;
 
   screen_locker_ = NULL;
   bool state = false;