[cros Aura] Added modal container for screen lock.

ui/aura_shell/stacking_controller.cc

Index: ui/aura_shell/stacking_controller.cc
diff --git a/ui/aura_shell/stacking_controller.cc b/ui/aura_shell/stacking_controller.cc
index ffe5cb4af7cb8101de55cd0accca44598d297604..b1595fda47db7f791b061992443a4004fb2cb088 100644
--- a/ui/aura_shell/stacking_controller.cc
+++ b/ui/aura_shell/stacking_controller.cc
@@ -23,7 +23,8 @@ aura::Window* GetContainer(int id) {
 bool SupportsChildActivation(aura::Window* window) {
   return window->id() == kShellWindowId_DefaultContainer ||
          window->id() == kShellWindowId_AlwaysOnTopContainer ||
-         window->id() == kShellWindowId_ModalContainer;
+         window->id() == kShellWindowId_ModalContainer ||
+         window->id() == kShellWindowId_LockModalContainer;
 }
 
 bool IsWindowModal(aura::Window* window) {
@@ -75,7 +76,13 @@ void StackingController::AddChildToDefaultParent(aura::Window* window) {
     case aura::WINDOW_TYPE_NORMAL:
     case aura::WINDOW_TYPE_POPUP:
       if (IsWindowModal(window)) {
-        parent = GetContainer(internal::kShellWindowId_ModalContainer);
+        aura::Window* lock_container =
+            GetContainer(internal::kShellWindowId_LockScreenContainer);
+        // Lock/login screen has its own modal container.
+        if (!lock_container->children().size())

[Ben Goodger (Google), 2011/11/28 17:12:56]

I realized there is a flaw here that will require some more complexity.

If the modal window is coming from a window behind the lock screen (consider a
page showing a js modal alert), then showing the modal dialog above the lock
screen would violate the privacy of the user whose session was locked.

Thus the following makes sense to me:

When a lock screen is active, modal dialogs opened from content in containers
behind the lock screen should still open in the regular modal container. The
event filter there would be superceded by the event filter attached to the lock
screen since the lock screen one is in front of it in the z-index and is thus
consulted first.

Modal windows opened from content in the lock container, or any container in
front of it, would be opened in the lock modal container.

So, I think you'll have to write a little more code here (perhaps move out to a
separate function since this function is going to be pretty long otherwise)...
and adjust your tests to consider both these cases.

[Nikita (slow), 2011/11/29 10:06:34]

Done.

+          parent = GetContainer(internal::kShellWindowId_ModalContainer);
+        else
+          parent = GetContainer(internal::kShellWindowId_LockModalContainer);
         break;
       }
       parent = always_on_top_controller_->GetContainer(window);