Don't activate a window if screen is locked.

ash/wm/activation_controller.cc

Index: ash/wm/activation_controller.cc
diff --git a/ash/wm/activation_controller.cc b/ash/wm/activation_controller.cc
index 5ea7466c0f2a1a89222bf5f6b029fa1b0bbc7805..794452d8531169beb82ac25cc98d142c4fae05b2 100644
--- a/ash/wm/activation_controller.cc
+++ b/ash/wm/activation_controller.cc
@@ -40,7 +40,7 @@ bool SupportsChildActivation(aura::Window* window) {
 // supports activation/deactivation.
 bool CanActivateWindow(aura::Window* window) {
   return window &&
-      window->IsVisible() &&
+      window->CanReceiveEvents() &&

[sky, 2012/01/12 21:11:36]

One downside of this is that if the lock screen is up, this will return false,
which will prevent the window from coming to the front so that when the lock
screen goes away it is deactivated. Maybe we should move the window to the front
but not activate it.

[oshima, 2012/01/12 21:32:50]

good point. done.

       (!aura::client::GetActivationDelegate(window) ||
         aura::client::GetActivationDelegate(window)->ShouldActivate(NULL)) &&
       SupportsChildActivation(window->parent());