Check if there is no window in LockSystemModalContainer when unlocked.

ash/shell.cc

Index: ash/shell.cc
diff --git a/ash/shell.cc b/ash/shell.cc
index 1bade434dd44a35b45a7547c5bd7dd0329067b33..6842cfc3bc316a98f03ee7ee96dd8cfeda0648c2 100644
--- a/ash/shell.cc
+++ b/ash/shell.cc
@@ -743,6 +743,16 @@ void Shell::OnAppTerminating() {
 
 void Shell::OnLockStateChanged(bool locked) {
   FOR_EACH_OBSERVER(ShellObserver, observers_, OnLockStateChanged(locked));
+  // Make sure that there is no system modal in Lock layer when unlocked.
+  if (!locked) {
+    std::vector<aura::Window*> containers = GetContainersFromAllRootWindows(
+        internal::kShellWindowId_LockSystemModalContainer,
+        GetPrimaryRootWindow());
+    for (std::vector<aura::Window*>::const_iterator iter = containers.begin();
+         iter != containers.end(); ++iter) {
+      DCHECK_EQ(0u, (*iter)->children().size());

[James Cook, 2013/08/09 19:08:03]

Do you want DCHECK or CHECK here?  Are you trying to find problems on actual
devices in the field?

If you stick with DCHECK, maybe wrap this code in #ifdef NDEBUG so we don't do
the loop iteration for a no-op DCHECK.

+    }
+  }
 }
 
 void Shell::CreateLauncher() {