Per-display resumed activities

Allow each display to have its own resumed activity. The focus is
defined by Z-order of displays reported from WindowManager.

Bug: 111541062
Test: ActivityManagerMultiDisplayTests
Change-Id: I347dcfcd1e34f4db985b7d9a649b0a1e6b730eee
diff --git a/services/core/java/com/android/server/am/KeyguardController.java b/services/core/java/com/android/server/am/KeyguardController.java
index e345b4d..ee4e36f 100644
--- a/services/core/java/com/android/server/am/KeyguardController.java
+++ b/services/core/java/com/android/server/am/KeyguardController.java
@@ -163,7 +163,7 @@
             updateKeyguardSleepToken();
 
             // Some stack visibility might change (e.g. docked stack)
-            mStackSupervisor.resumeFocusedStackTopActivityLocked();
+            mStackSupervisor.resumeFocusedStacksTopActivitiesLocked();
             mStackSupervisor.ensureActivitiesVisibleLocked(null, 0, !PRESERVE_WINDOWS);
             mStackSupervisor.addStartingWindowsForVisibleActivities(true /* taskSwitch */);
             mWindowManager.executeAppTransition();