diff --git a/core/java/android/app/ActivityManager.java b/core/java/android/app/ActivityManager.java
index 3bfeff0..6ae32d0 100644
--- a/core/java/android/app/ActivityManager.java
+++ b/core/java/android/app/ActivityManager.java
@@ -434,10 +434,17 @@
     public static final int DOCKED_STACK_ID = FREEFORM_WORKSPACE_STACK_ID + 1;
 
     /**
+     * ID of stack that always on top (always visible) when it exist.
+     * Mainly used for this in Picture-in-Picture mode.
+     * @hide
+     */
+    public static final int PINNED_STACK_ID = DOCKED_STACK_ID + 1;
+
+    /**
      * Last static stack stack ID.
      * @hide
      */
-    public static final int LAST_STATIC_STACK_ID = DOCKED_STACK_ID;
+    public static final int LAST_STATIC_STACK_ID = PINNED_STACK_ID;
 
     /**
      * Start of ID range used by stacks that are created dynamically.
diff --git a/core/java/com/android/internal/policy/PhoneWindow.java b/core/java/com/android/internal/policy/PhoneWindow.java
index 4644211..afef763 100644
--- a/core/java/com/android/internal/policy/PhoneWindow.java
+++ b/core/java/com/android/internal/policy/PhoneWindow.java
@@ -20,6 +20,7 @@
 import static android.app.ActivityManager.FREEFORM_WORKSPACE_STACK_ID;
 import static android.app.ActivityManager.FULLSCREEN_WORKSPACE_STACK_ID;
 import static android.app.ActivityManager.INVALID_STACK_ID;
+import static android.app.ActivityManager.PINNED_STACK_ID;
 import static android.view.View.MeasureSpec.AT_MOST;
 import static android.view.View.MeasureSpec.EXACTLY;
 import static android.view.View.MeasureSpec.getMode;
@@ -5408,7 +5409,7 @@
      * @Return Returns true if the window should show a non client decor.
      **/
     private static boolean hasNonClientDecor(int workspaceId) {
-        return workspaceId == FREEFORM_WORKSPACE_STACK_ID;
+        return workspaceId == FREEFORM_WORKSPACE_STACK_ID || workspaceId == PINNED_STACK_ID;
     }
 
     /**
@@ -5417,7 +5418,7 @@
      * @Return Returns true if the window should show a shadow.
      **/
     private static boolean nonClientDecorHasShadow(int workspaceId) {
-        return workspaceId == FREEFORM_WORKSPACE_STACK_ID;
+        return workspaceId == FREEFORM_WORKSPACE_STACK_ID || workspaceId == PINNED_STACK_ID;
     }
 
     @Override
diff --git a/services/core/java/com/android/server/am/ActivityManagerService.java b/services/core/java/com/android/server/am/ActivityManagerService.java
index c728b39..43e45e1 100644
--- a/services/core/java/com/android/server/am/ActivityManagerService.java
+++ b/services/core/java/com/android/server/am/ActivityManagerService.java
@@ -24,6 +24,7 @@
 import static android.app.ActivityManager.FULLSCREEN_WORKSPACE_STACK_ID;
 import static android.app.ActivityManager.HOME_STACK_ID;
 import static android.app.ActivityManager.INVALID_STACK_ID;
+import static android.app.ActivityManager.PINNED_STACK_ID;
 import static android.app.ActivityManager.RESIZE_MODE_PRESERVE_WINDOW;
 import static android.content.pm.PackageManager.PERMISSION_GRANTED;
 import static com.android.internal.util.XmlUtils.readBooleanAttribute;
@@ -8638,9 +8639,10 @@
                 // - a non-null bounds on a non-freeform (fullscreen OR docked) task moves
                 //   that task to freeform
                 // - otherwise the task is not moved
-                // Note it's not allowed to resize a home stack task, or a docked task.
+                // Note it's not allowed to resize a home, docked, or pinned stack task.
                 int stackId = task.stack.mStackId;
-                if (stackId == HOME_STACK_ID || stackId == DOCKED_STACK_ID) {
+                if (stackId == HOME_STACK_ID || stackId == DOCKED_STACK_ID
+                        || stackId == PINNED_STACK_ID) {
                     throw new IllegalArgumentException("trying to resizeTask on a "
                             + "home or docked task");
                 }
diff --git a/services/core/java/com/android/server/am/ActivityStack.java b/services/core/java/com/android/server/am/ActivityStack.java
index 8bf1d22..ed3a1c2 100644
--- a/services/core/java/com/android/server/am/ActivityStack.java
+++ b/services/core/java/com/android/server/am/ActivityStack.java
@@ -22,6 +22,7 @@
 import static android.app.ActivityManager.FULLSCREEN_WORKSPACE_STACK_ID;
 import static android.app.ActivityManager.HOME_STACK_ID;
 import static android.app.ActivityManager.LAST_STATIC_STACK_ID;
+import static android.app.ActivityManager.PINNED_STACK_ID;
 import static android.content.pm.ActivityInfo.FLAG_SHOW_FOR_ALL_USERS;
 
 import static com.android.server.am.ActivityManagerDebugConfig.*;
@@ -253,6 +254,9 @@
 
     private final LaunchingTaskPositioner mTaskPositioner;
 
+    // If the bounds of task contained in this stack should be persisted across power cycles.
+    final boolean mPersistTaskBounds;
+
     static final int PAUSE_TIMEOUT_MSG = ActivityManagerService.FIRST_ACTIVITY_STACK_MSG + 1;
     static final int DESTROY_TIMEOUT_MSG = ActivityManagerService.FIRST_ACTIVITY_STACK_MSG + 2;
     static final int LAUNCH_TICK_MSG = ActivityManagerService.FIRST_ACTIVITY_STACK_MSG + 3;
@@ -354,10 +358,6 @@
         return count;
     }
 
-    int numTasks() {
-        return mTaskHistory.size();
-    }
-
     ActivityStack(ActivityStackSupervisor.ActivityContainer activityContainer,
             RecentTasks recentTasks) {
         mActivityContainer = activityContainer;
@@ -370,6 +370,7 @@
         mRecentTasks = recentTasks;
         mTaskPositioner = mStackId == FREEFORM_WORKSPACE_STACK_ID
                 ? new LaunchingTaskPositioner() : null;
+        mPersistTaskBounds = mStackId != DOCKED_STACK_ID && mStackId != PINNED_STACK_ID;
     }
 
     void attachDisplay(ActivityStackSupervisor.ActivityDisplay activityDisplay, boolean onTop) {
@@ -1306,6 +1307,11 @@
             return true;
         }
 
+        if (mStackId == PINNED_STACK_ID) {
+            // Pinned stack is always visible if it exist.
+            return true;
+        }
+
         final int stackIndex = mStacks.indexOf(this);
 
         if (stackIndex == mStacks.size() - 1) {
@@ -1328,8 +1334,9 @@
         }
 
         final int belowFocusedIndex = mStacks.indexOf(focusedStack) - 1;
-        if (focusedStackId == DOCKED_STACK_ID && stackIndex == belowFocusedIndex) {
-            // Stacks directly behind the docked stack are always visible.
+        if ((focusedStackId == DOCKED_STACK_ID || focusedStackId == PINNED_STACK_ID)
+                && stackIndex == belowFocusedIndex) {
+            // Stacks directly behind the docked or pinned stack are always visible.
             return true;
         }
 
@@ -1343,9 +1350,10 @@
             }
             if (belowFocusedIndex >= 0) {
                 final ActivityStack stack = mStacks.get(belowFocusedIndex);
-                if (stack.mStackId == DOCKED_STACK_ID && stackIndex == (belowFocusedIndex - 1)) {
-                    // The stack behind the docked stack is also visible so we can have a complete
-                    // backdrop to the translucent activity when the docked stack is up.
+                if ((stack.mStackId == DOCKED_STACK_ID || stack.mStackId == PINNED_STACK_ID)
+                        && stackIndex == (belowFocusedIndex - 1)) {
+                    // The stack behind the docked or pinned stack is also visible so we can have a
+                    // complete backdrop to the translucent activity when the docked stack is up.
                     return true;
                 }
             }
@@ -2784,9 +2792,10 @@
             final String myReason = reason + " adjustFocus";
             if (next != r) {
                 if (next != null && (mStackId == FREEFORM_WORKSPACE_STACK_ID
-                        || mStackId == DOCKED_STACK_ID)) {
-                    // For freeform and docked stacks we always keep the focus within the stack as
-                    // long as there is a running activity in the stack that we can adjust focus to.
+                        || mStackId == DOCKED_STACK_ID || mStackId == PINNED_STACK_ID)) {
+                    // For freeform, docked, and pinned stacks we always keep the focus within the
+                    // stack as long as there is a running activity in the stack that we can adjust
+                    // focus to.
                     mService.setFocusedActivityLocked(next, myReason);
                     return;
                 } else {
diff --git a/services/core/java/com/android/server/am/ActivityStackSupervisor.java b/services/core/java/com/android/server/am/ActivityStackSupervisor.java
index 99f7ec6..33f8da7 100644
--- a/services/core/java/com/android/server/am/ActivityStackSupervisor.java
+++ b/services/core/java/com/android/server/am/ActivityStackSupervisor.java
@@ -3293,7 +3293,8 @@
             return;
         }
         final String reason = "moveTaskToStack";
-        if (stackId == DOCKED_STACK_ID || stackId == FULLSCREEN_WORKSPACE_STACK_ID) {
+        if (stackId == DOCKED_STACK_ID || stackId == PINNED_STACK_ID
+                || stackId == FULLSCREEN_WORKSPACE_STACK_ID) {
             // We are about to relaunch the activity because its configuration changed due to
             // being maximized, i.e. size change. The activity will first remove the old window
             // and then add a new one. This call will tell window manager about this, so it can
@@ -3314,7 +3315,7 @@
                 && task.mBounds == null && task.mLastNonFullscreenBounds != null) {
             resizeTaskLocked(task, task.mLastNonFullscreenBounds,
                     RESIZE_MODE_SYSTEM, !PRESERVE_WINDOWS);
-        } else if (stackId == DOCKED_STACK_ID) {
+        } else if (stackId == DOCKED_STACK_ID || stackId == PINNED_STACK_ID) {
             resizeTaskLocked(task, stack.mBounds,
                     RESIZE_MODE_SYSTEM, !PRESERVE_WINDOWS);
         }
diff --git a/services/core/java/com/android/server/am/TaskRecord.java b/services/core/java/com/android/server/am/TaskRecord.java
index fe87a93..090a342 100644
--- a/services/core/java/com/android/server/am/TaskRecord.java
+++ b/services/core/java/com/android/server/am/TaskRecord.java
@@ -20,6 +20,7 @@
 import static android.app.ActivityManager.FREEFORM_WORKSPACE_STACK_ID;
 import static android.app.ActivityManager.FULLSCREEN_WORKSPACE_STACK_ID;
 import static android.app.ActivityManager.HOME_STACK_ID;
+import static android.app.ActivityManager.PINNED_STACK_ID;
 import static android.content.Intent.FLAG_ACTIVITY_NEW_DOCUMENT;
 import static android.content.Intent.FLAG_ACTIVITY_RETAIN_IN_RECENTS;
 import static android.content.pm.ActivityInfo.LOCK_TASK_LAUNCH_MODE_ALWAYS;
@@ -1189,14 +1190,14 @@
 
         mFullscreen = bounds == null;
         if (mFullscreen) {
-            if (mBounds != null && stack.mStackId != DOCKED_STACK_ID) {
+            if (mBounds != null && stack.mPersistTaskBounds) {
                 mLastNonFullscreenBounds = mBounds;
             }
             mBounds = null;
             mOverrideConfig = Configuration.EMPTY;
         } else {
             mBounds = new Rect(bounds);
-            if (stack == null || stack.mStackId != DOCKED_STACK_ID) {
+            if (stack == null || stack.mPersistTaskBounds) {
                 mLastNonFullscreenBounds = mBounds;
             }
 
@@ -1235,11 +1236,12 @@
 
     /** Returns the bounds that should be used to launch this task. */
     Rect getLaunchBounds() {
+        final int stackId = stack.mStackId;
         if (stack == null
-                || stack.mStackId == HOME_STACK_ID
-                || stack.mStackId == FULLSCREEN_WORKSPACE_STACK_ID) {
+                || stackId == HOME_STACK_ID
+                || stackId == FULLSCREEN_WORKSPACE_STACK_ID) {
             return (mResizeable && stack != null) ? stack.mBounds : null;
-        } else if (stack.mStackId == DOCKED_STACK_ID) {
+        } else if (!stack.mPersistTaskBounds) {
             return stack.mBounds;
         }
         return mLastNonFullscreenBounds;
diff --git a/services/core/java/com/android/server/wm/Task.java b/services/core/java/com/android/server/wm/Task.java
index 7c56180..6527881 100644
--- a/services/core/java/com/android/server/wm/Task.java
+++ b/services/core/java/com/android/server/wm/Task.java
@@ -17,12 +17,14 @@
 package com.android.server.wm;
 
 import static android.app.ActivityManager.DOCKED_STACK_ID;
+import static android.app.ActivityManager.FREEFORM_WORKSPACE_STACK_ID;
+import static android.app.ActivityManager.PINNED_STACK_ID;
 import static android.app.ActivityManager.RESIZE_MODE_SYSTEM_SCREEN_ROTATION;
 import static com.android.server.wm.WindowManagerService.TAG;
 import static com.android.server.wm.WindowManagerService.DEBUG_RESIZE;
 import static com.android.server.wm.WindowManagerService.DEBUG_STACK;
 import static com.android.server.wm.WindowManagerService.H.RESIZE_TASK;
-import static android.app.ActivityManager.FREEFORM_WORKSPACE_STACK_ID;
+
 
 import android.content.res.Configuration;
 import android.graphics.Rect;
@@ -187,7 +189,8 @@
                 bounds = mTmpRect;
                 mFullscreen = true;
             } else {
-                if (mStack.mStackId != FREEFORM_WORKSPACE_STACK_ID || bounds.isEmpty()) {
+                if ((mStack.mStackId != FREEFORM_WORKSPACE_STACK_ID
+                        && mStack.mStackId != PINNED_STACK_ID) || bounds.isEmpty()) {
                     // ensure bounds are entirely within the display rect
                     if (!bounds.intersect(mTmpRect)) {
                         // Can't set bounds outside the containing display...Sorry!
@@ -241,8 +244,7 @@
     private boolean useCurrentBounds() {
         final DisplayContent displayContent = mStack.getDisplayContent();
         if (mFullscreen
-                || mStack.mStackId == FREEFORM_WORKSPACE_STACK_ID
-                || mStack.mStackId == DOCKED_STACK_ID
+                || mStack.allowTaskResize()
                 || displayContent == null
                 || displayContent.getDockedStackLocked() != null) {
             return true;
diff --git a/services/core/java/com/android/server/wm/TaskStack.java b/services/core/java/com/android/server/wm/TaskStack.java
index 6734fd6..9b3d478 100644
--- a/services/core/java/com/android/server/wm/TaskStack.java
+++ b/services/core/java/com/android/server/wm/TaskStack.java
@@ -22,6 +22,7 @@
 import static android.app.ActivityManager.FREEFORM_WORKSPACE_STACK_ID;
 import static android.app.ActivityManager.FULLSCREEN_WORKSPACE_STACK_ID;
 import static android.app.ActivityManager.LAST_STATIC_STACK_ID;
+import static android.app.ActivityManager.PINNED_STACK_ID;
 import static com.android.server.wm.WindowManagerService.DEBUG_TASK_MOVEMENT;
 import static com.android.server.wm.WindowManagerService.H.RESIZE_STACK;
 import static com.android.server.wm.WindowManagerService.TAG;
@@ -123,7 +124,8 @@
 
     boolean allowTaskResize() {
         return mStackId == FREEFORM_WORKSPACE_STACK_ID
-                || mStackId == DOCKED_STACK_ID;
+                || mStackId == DOCKED_STACK_ID
+                || mStackId == PINNED_STACK_ID;
     }
 
     /**
@@ -202,6 +204,7 @@
     private boolean useCurrentBounds() {
         if (mFullscreen
                 || mStackId == DOCKED_STACK_ID
+                || mStackId == PINNED_STACK_ID
                 || mDisplayContent == null
                 || mDisplayContent.getDockedStackLocked() != null) {
             return true;
@@ -393,7 +396,7 @@
 
         Rect bounds = null;
         final TaskStack dockedStack = mService.mStackIdToStack.get(DOCKED_STACK_ID);
-        if (mStackId == DOCKED_STACK_ID || (dockedStack != null
+        if (mStackId == DOCKED_STACK_ID || (dockedStack != null && mStackId != PINNED_STACK_ID
                 && mStackId >= FIRST_STATIC_STACK_ID && mStackId <= LAST_STATIC_STACK_ID)) {
             // The existence of a docked stack affects the size of any static stack created since
             // the docked stack occupies a dedicated region on screen.
@@ -422,6 +425,7 @@
 
     void getStackDockedModeBoundsLocked(Rect outBounds) {
         if (mStackId == DOCKED_STACK_ID
+                || mStackId == PINNED_STACK_ID
                 || mStackId > LAST_STATIC_STACK_ID
                 || mDisplayContent == null) {
             outBounds.set(mBounds);
@@ -533,7 +537,7 @@
         for (int i = 0; i < count; i++) {
             final TaskStack otherStack = mService.mStackIdToStack.valueAt(i);
             final int otherStackId = otherStack.mStackId;
-            if (otherStackId != DOCKED_STACK_ID
+            if (otherStackId != DOCKED_STACK_ID && mStackId != PINNED_STACK_ID
                     && otherStackId >= FIRST_STATIC_STACK_ID
                     && otherStackId <= LAST_STATIC_STACK_ID) {
                 mService.mH.sendMessage(