mash: Use ash shell window container ids instead of ash::mojom::Container

I need to use additional window containers in a subsequent CL. Rather than
continue to maintain a mapping of kShellWindowId_Foo to ash::mojom::Container,
just use the ash container ids natively.

* Add kInitialContainerId_Property to window_manager.mojom, which is where we
set initial bounds and initial display.
* Remove container.mojom and associated utility functions.
* Replace usage of Container::LOGIN_WINDOW with LockScreenContainer, which is
where the windows end up.
* Ditto for Container::OVERLAY.
* Move ash/common/shell_window_ids.h to ash/public/cpp/

BUG=647412
TEST=compiles, chrome --mash --login-manager shows login dialogs correctly
[email protected] for exo

Review-Url: https://chromiumcodereview.appspot.com/2430593002
Cr-Commit-Position: refs/heads/master@{#426161}
diff --git a/ash/extended_desktop_unittest.cc b/ash/extended_desktop_unittest.cc
index 9961be6a..ebdb540 100644
--- a/ash/extended_desktop_unittest.cc
+++ b/ash/extended_desktop_unittest.cc
@@ -3,10 +3,10 @@
 // found in the LICENSE file.
 
 #include "ash/aura/wm_window_aura.h"
-#include "ash/common/shell_window_ids.h"
 #include "ash/common/system/tray/system_tray.h"
 #include "ash/common/wm/root_window_finder.h"
 #include "ash/display/display_manager.h"
+#include "ash/public/cpp/shell_window_ids.h"
 #include "ash/root_window_controller.h"
 #include "ash/shell.h"
 #include "ash/test/ash_test_base.h"