All Apps transition with gradient and scrim.

The transition is behind a feature flag and
turned off by default.

Change-Id: I155840ba82b5a573d874376797db5f739a52d706

src/com/android/launcher3/allapps/AllAppsContainerView.java

@@ -492,7 +492,8 @@ public class AllAppsContainerView extends BaseContainerView implements DragSourc
             ViewGroup.LayoutParams navBarBgLp = navBarBg.getLayoutParams();
             navBarBgLp.height = insets.bottom;
             navBarBg.setLayoutParams(navBarBgLp);
-            navBarBg.setVisibility(View.VISIBLE);
+            navBarBg.setVisibility(FeatureFlags.LAUNCHER3_GRADIENT_ALL_APPS
+                    ? View.INVISIBLE : View.VISIBLE);
         }
     }