diff --git a/services/core/java/com/android/server/wm/DisplayContent.java b/services/core/java/com/android/server/wm/DisplayContent.java
index 8bbc5a9..da7eeb0 100644
--- a/services/core/java/com/android/server/wm/DisplayContent.java
+++ b/services/core/java/com/android/server/wm/DisplayContent.java
@@ -244,20 +244,19 @@
         mTapDetector.setTouchExcludeRegion(mTouchExcludeRegion);
     }
 
-    void switchUserStacks(int newUserId) {
+    void switchUserStacks() {
         final WindowList windows = getWindowList();
         for (int i = 0; i < windows.size(); i++) {
             final WindowState win = windows.get(i);
             if (win.isHiddenFromUserLocked()) {
-                if (DEBUG_VISIBILITY) Slog.w(TAG, "user changing " + newUserId + " hiding "
-                        + win + ", attrs=" + win.mAttrs.type + ", belonging to "
-                        + win.mOwnerUid);
+                if (DEBUG_VISIBILITY) Slog.w(TAG, "user changing, hiding " + win
+                        + ", attrs=" + win.mAttrs.type + ", belonging to " + win.mOwnerUid);
                 win.hideLw(false);
             }
         }
 
         for (int stackNdx = mStacks.size() - 1; stackNdx >= 0; --stackNdx) {
-            mStacks.get(stackNdx).switchUser(newUserId);
+            mStacks.get(stackNdx).switchUser();
         }
     }
 
diff --git a/services/core/java/com/android/server/wm/TaskStack.java b/services/core/java/com/android/server/wm/TaskStack.java
index c677e2c..8988a91 100644
--- a/services/core/java/com/android/server/wm/TaskStack.java
+++ b/services/core/java/com/android/server/wm/TaskStack.java
@@ -420,18 +420,24 @@
 
     void startDimmingIfNeeded(WindowStateAnimator newWinAnimator) {
         // Only set dim params on the highest dimmed layer.
-        final WindowStateAnimator existingDimWinAnimator = mDimWinAnimator;
         // Don't turn on for an unshown surface, or for any layer but the highest dimmed layer.
-        if (newWinAnimator.mSurfaceShown && (existingDimWinAnimator == null
-                || !existingDimWinAnimator.mSurfaceShown
-                || existingDimWinAnimator.mAnimLayer < newWinAnimator.mAnimLayer)) {
+        if (newWinAnimator.mSurfaceShown && (mDimWinAnimator == null
+                || !mDimWinAnimator.mSurfaceShown
+                || mDimWinAnimator.mAnimLayer < newWinAnimator.mAnimLayer)) {
             mDimWinAnimator = newWinAnimator;
+            if (mDimWinAnimator.mWin.mAppToken == null
+                    && !mFullscreen && mDisplayContent != null) {
+                // Dim should cover the entire screen for system windows.
+                mDisplayContent.getLogicalDisplayRect(mTmpRect);
+                mDimLayer.setBounds(mTmpRect);
+            }
         }
     }
 
     void stopDimmingIfNeeded() {
         if (!mDimmingTag && isDimming()) {
             mDimWinAnimator = null;
+            mDimLayer.setBounds(mBounds);
         }
     }
 
@@ -446,7 +452,7 @@
         }
     }
 
-    void switchUser(int userId) {
+    void switchUser() {
         int top = mTasks.size();
         for (int taskNdx = 0; taskNdx < top; ++taskNdx) {
             Task task = mTasks.get(taskNdx);
@@ -475,7 +481,7 @@
         }
         if (mDimLayer.isDimming()) {
             pw.print(prefix); pw.println("mDimLayer:");
-            mDimLayer.printTo(prefix, pw);
+            mDimLayer.printTo(prefix + " ", pw);
             pw.print(prefix); pw.print("mDimWinAnimator="); pw.println(mDimWinAnimator);
         }
         if (!mExitingAppTokens.isEmpty()) {
diff --git a/services/core/java/com/android/server/wm/WindowManagerService.java b/services/core/java/com/android/server/wm/WindowManagerService.java
index 02a4f4d..8e3adf1 100644
--- a/services/core/java/com/android/server/wm/WindowManagerService.java
+++ b/services/core/java/com/android/server/wm/WindowManagerService.java
@@ -5479,7 +5479,7 @@
             final int numDisplays = mDisplayContents.size();
             for (int displayNdx = 0; displayNdx < numDisplays; ++displayNdx) {
                 final DisplayContent displayContent = mDisplayContents.valueAt(displayNdx);
-                displayContent.switchUserStacks(newUserId);
+                displayContent.switchUserStacks();
                 rebuildAppWindowListLocked(displayContent);
             }
             performLayoutAndPlaceSurfacesLocked();