Initial changes to support blur

- Add a new controller to update the background blur on either the
  launcher or app surfaces based on state or transition

Bug: 149792636

Change-Id: I6103cd3d53a00c8025558dd49bb73137e2980014

quickstep/src/com/android/launcher3/BaseQuickstepLauncher.java

@@ -234,6 +234,7 @@ public abstract class BaseQuickstepLauncher extends Launcher
         return new StateHandler[] {
                 getAllAppsController(),
                 getWorkspace(),
+                getBackgroundBlurController(),
                 new RecentsViewStateController(this),
                 new BackButtonAlphaHandler(this)};
     }