Animation for docking task gesture

- Don't move recents window around during the animation
- Set the correct task size shortly after docking, so recents
starts with the correct size to avoid jank.
- Add staggered animation in recents.

Bug: 27154882
Change-Id: I7c56102feba9c3f6cb86cb5f1d87f0ad3b29c721
diff --git a/services/core/java/com/android/server/am/ActivityStack.java b/services/core/java/com/android/server/am/ActivityStack.java
index e50722a..2f5018d 100644
--- a/services/core/java/com/android/server/am/ActivityStack.java
+++ b/services/core/java/com/android/server/am/ActivityStack.java
@@ -414,6 +414,12 @@
             mTaskPositioner.reset();
         }
         mWindowManager.detachStack(mStackId);
+        if (mStackId == DOCKED_STACK_ID) {
+            // If we removed a docked stack we want to resize it so it resizes all other stacks
+            // in the system to fullscreen.
+            mStackSupervisor.resizeDockedStackLocked(
+                    null, null, null, null, null, PRESERVE_WINDOWS);
+        }
     }
 
     public void getDisplaySize(Point out) {