Disable PiP when a task is locked.

Bug: 37135610
Test: Start PiP, enable screen pinning, ensure that PiP is dismissed.
Change-Id: Ie5165364db891b13dd4ef282089f915fe9f99615
diff --git a/services/core/java/com/android/server/am/ActivityManagerService.java b/services/core/java/com/android/server/am/ActivityManagerService.java
index d43fa01..8f1afa8 100644
--- a/services/core/java/com/android/server/am/ActivityManagerService.java
+++ b/services/core/java/com/android/server/am/ActivityManagerService.java
@@ -10685,6 +10685,13 @@
             return;
         }
 
+        // When a task is locked, dismiss the pinned stack if it exists
+        final PinnedActivityStack pinnedStack = mStackSupervisor.getStack(
+                PINNED_STACK_ID);
+        if (pinnedStack != null) {
+            mStackSupervisor.removeStackLocked(PINNED_STACK_ID);
+        }
+
         // isSystemInitiated is used to distinguish between locked and pinned mode, as pinned mode
         // is initiated by system after the pinning request was shown and locked mode is initiated
         // by an authorized app directly