Removing ContentObserver in launcher

> Using callback insted of using a content observer
> Setting the listener in LauncherAppState to prevent resource leak

Change-Id: Id23a4d5c8812e86178997e536226e09ec3740f84

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

@@ -56,7 +56,7 @@ final class DefaultAppSearchController extends AllAppsSearchBarController
     private View mDismissSearchButtonView;
     @Thunk AllAppsSearchEditView mSearchBarEditView;
     @Thunk AllAppsRecyclerView mAppsRecyclerView;
-    private Runnable mFocusRecyclerViewRunnable = new Runnable() {
+    @Thunk Runnable mFocusRecyclerViewRunnable = new Runnable() {
         @Override
         public void run() {
             mAppsRecyclerView.requestFocus();