Hiding pinned stack tasks from overview

Bug: 25381158
Change-Id: Iad442b7f5dc49109529cb5dab2168b19837af6e3
diff --git a/services/core/java/com/android/server/am/ActivityStack.java b/services/core/java/com/android/server/am/ActivityStack.java
index 59acccd..582a1fe 100644
--- a/services/core/java/com/android/server/am/ActivityStack.java
+++ b/services/core/java/com/android/server/am/ActivityStack.java
@@ -520,6 +520,14 @@
         return mStackId == HOME_STACK_ID;
     }
 
+    final boolean isDockedStack() {
+        return mStackId == DOCKED_STACK_ID;
+    }
+
+    final boolean isPinnedStack() {
+        return mStackId == PINNED_STACK_ID;
+    }
+
     final boolean isOnHomeDisplay() {
         return isAttached() &&
                 mActivityContainer.mActivityDisplay.mDisplayId == Display.DEFAULT_DISPLAY;