Dim background when group notification expanded

This fixes the contrast issue when dismissing

Fixes: 187652080
Test: visual
Change-Id: Ic181bc8b23ae62c8212fee19fd7c6434eb94cd61
diff --git a/packages/SystemUI/src/com/android/systemui/statusbar/notification/row/ActivatableNotificationView.java b/packages/SystemUI/src/com/android/systemui/statusbar/notification/row/ActivatableNotificationView.java
index c24c2be..4f3406c 100644
--- a/packages/SystemUI/src/com/android/systemui/statusbar/notification/row/ActivatableNotificationView.java
+++ b/packages/SystemUI/src/com/android/systemui/statusbar/notification/row/ActivatableNotificationView.java
@@ -203,6 +203,14 @@
         mBackgroundNormal.setCustomBackground(R.drawable.notification_material_bg);
     }
 
+    protected boolean hideBackground() {
+        return false;
+    }
+
+    protected void updateBackground() {
+        mBackgroundNormal.setVisibility(hideBackground() ? INVISIBLE : VISIBLE);
+    }
+
 
     @Override
     public boolean onInterceptTouchEvent(MotionEvent ev) {
diff --git a/packages/SystemUI/src/com/android/systemui/statusbar/notification/row/ExpandableNotificationRow.java b/packages/SystemUI/src/com/android/systemui/statusbar/notification/row/ExpandableNotificationRow.java
index ba28dc5..9d56e9b 100644
--- a/packages/SystemUI/src/com/android/systemui/statusbar/notification/row/ExpandableNotificationRow.java
+++ b/packages/SystemUI/src/com/android/systemui/statusbar/notification/row/ExpandableNotificationRow.java
@@ -2890,6 +2890,12 @@
             mShowNoBackground = false;
         }
         updateOutline();
+        updateBackground();
+    }
+
+    @Override
+    protected boolean hideBackground() {
+        return mShowNoBackground || super.hideBackground();
     }
 
     public int getPositionOfChild(ExpandableNotificationRow childRow) {