Fix build breakage with ag/2997247

Test: Builds
Bug: 65612427
Change-Id: Icacb44733a84a530dcea459209aac705ff837e22
diff --git a/services/core/java/com/android/server/wm/DisplayContent.java b/services/core/java/com/android/server/wm/DisplayContent.java
index 91cce31..bdf46c7 100644
--- a/services/core/java/com/android/server/wm/DisplayContent.java
+++ b/services/core/java/com/android/server/wm/DisplayContent.java
@@ -18,6 +18,7 @@
 
 import static android.app.ActivityManager.StackId.DOCKED_STACK_ID;
 import static android.app.ActivityManager.StackId.FREEFORM_WORKSPACE_STACK_ID;
+import static android.app.ActivityManager.StackId.PINNED_STACK_ID;
 import static android.app.WindowConfiguration.ACTIVITY_TYPE_UNDEFINED;
 import static android.app.WindowConfiguration.WINDOWING_MODE_FULLSCREEN;
 import static android.app.WindowConfiguration.WINDOWING_MODE_PINNED;