Hide taskbar background when notification shade is expanded

- In 3 button mode, don't hide the background but do ensure nav buttons are translated down when swiping to notificaitons from the home screen

Test: swipe down notifications, background hides in 0 button mode but not in 3 button mode
Fixes: 199163951
Change-Id: Ic70adc7d67b2ab7c92a2d5d846b9b259d1bd7bfc

quickstep/src/com/android/launcher3/taskbar/TaskbarDragLayerController.java

@@ -42,6 +42,8 @@ public class TaskbarDragLayerController {
     private final AnimatedFloat mBgTaskbar = new AnimatedFloat(this::updateBackgroundAlpha);
     private final AnimatedFloat mBgNavbar = new AnimatedFloat(this::updateBackgroundAlpha);
     private final AnimatedFloat mKeyguardBgTaskbar = new AnimatedFloat(this::updateBackgroundAlpha);
+    private final AnimatedFloat mNotificationShadeBgTaskbar = new AnimatedFloat(
+            this::updateBackgroundAlpha);
     // Used to hide our background color when someone else (e.g. ScrimView) is handling it.
     private final AnimatedFloat mBgOverride = new AnimatedFloat(this::updateBackgroundAlpha);
 
@@ -63,6 +65,7 @@ public class TaskbarDragLayerController {
         mControllers = controllers;
         mTaskbarDragLayer.init(new TaskbarDragLayerCallbacks());
         mKeyguardBgTaskbar.value = 1;
+        mNotificationShadeBgTaskbar.value = 1;
         mBgOverride.value = 1;
     }
 
@@ -92,6 +95,10 @@ public class TaskbarDragLayerController {
         return mKeyguardBgTaskbar;
     }
 
+    public AnimatedFloat getNotificationShadeBgTaskbar() {
+        return mNotificationShadeBgTaskbar;
+    }
+
     public AnimatedFloat getOverrideBackgroundAlpha() {
         return mBgOverride;
     }
@@ -102,7 +109,8 @@ public class TaskbarDragLayerController {
 
     private void updateBackgroundAlpha() {
         final float bgNavbar = mBgNavbar.value;
-        final float bgTaskbar = mBgTaskbar.value * mKeyguardBgTaskbar.value;
+        final float bgTaskbar = mBgTaskbar.value * mKeyguardBgTaskbar.value
+                * mNotificationShadeBgTaskbar.value;
         mTaskbarDragLayer.setTaskbarBackgroundAlpha(
                 mBgOverride.value * Math.max(bgNavbar, bgTaskbar)
         );