Get dim bounds after super.prepareSurfaces

The dim state may be active when iterating child windows
from super.prepareSurfaces.

Bug: 159103089
Test: DimmerTests
Change-Id: I9326efa0e5d8f265ae7ec62434b850d43802c34e

services/core/java/com/android/server/wm/Dimmer.java

@@ -263,16 +263,19 @@ class Dimmer {
      * {@link WindowContainer#prepareSurfaces}. After calling this, the container should
      * chain {@link WindowContainer#prepareSurfaces} down to it's children to give them
      * a chance to request dims to continue.
-     * @return Non-null dim bounds if the dimmer is showing.
      */
-    Rect resetDimStates() {
+    void resetDimStates() {
         if (mDimState == null) {
-            return null;
+            return;
         }
         if (!mDimState.mDontReset) {
             mDimState.mDimming = false;
         }
-        return mDimState.mDimBounds;
+    }
+
+    /** Returns non-null bounds if the dimmer is showing. */
+    Rect getDimBounds() {
+        return mDimState != null ? mDimState.mDimBounds : null;
     }
 
     void dontAnimateExit() {

services/core/java/com/android/server/wm/DisplayArea.java

@@ -779,8 +779,9 @@ public class DisplayArea<T extends WindowContainer> extends WindowContainer<T> {
 
         @Override
         void prepareSurfaces() {
-            final Rect dimBounds = mDimmer.resetDimStates();
+            mDimmer.resetDimStates();
             super.prepareSurfaces();
+            final Rect dimBounds = mDimmer.getDimBounds();
             if (dimBounds != null) {
                 // Bounds need to be relative, as the dim layer is a child.
                 getBounds(dimBounds);

services/core/java/com/android/server/wm/Task.java

@@ -3253,9 +3253,10 @@ class Task extends TaskFragment {
 
     @Override
     void prepareSurfaces() {
-        final Rect dimBounds = mDimmer.resetDimStates();
+        mDimmer.resetDimStates();
         super.prepareSurfaces();
 
+        final Rect dimBounds = mDimmer.getDimBounds();
         if (dimBounds != null) {
             getDimBounds(dimBounds);
 

services/core/java/com/android/server/wm/TaskFragment.java

@@ -2923,9 +2923,10 @@ class TaskFragment extends WindowContainer<WindowContainer> {
             return;
         }
 
-        final Rect dimBounds = mDimmer.resetDimStates();
+        mDimmer.resetDimStates();
         super.prepareSurfaces();
 
+        final Rect dimBounds = mDimmer.getDimBounds();
         if (dimBounds != null) {
             // Bounds need to be relative, as the dim layer is a child.
             dimBounds.offsetTo(0 /* newLeft */, 0 /* newTop */);