[Bookmarks] Refactor search view to use SelectableListLayout paradigm

chrome/android/java/src/org/chromium/chrome/browser/bookmarks/BookmarkUIObserver.java

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package org.chromium.chrome.browser.bookmarks;
 
 import org.chromium.chrome.browser.widget.selection.SelectionDelegate.SelectionObserver;
 import org.chromium.components.bookmarks.BookmarkId;
 
 /**
  * Observer interface to get notification for UI mode changes, bookmark changes, and other related
  * event that affects UI. All bookmark UI components are expected to implement this and
  * update themselves correctly on each event.
  */
 interface BookmarkUIObserver extends SelectionObserver<BookmarkId> {
     void onBookmarkDelegateInitialized(BookmarkDelegate delegate);
 
     /**
      * Called when the entire UI is being destroyed and will be no longer in use.
      */
     void onDestroy();
 
     /**
      * @see BookmarkDelegate#openFolder(BookmarkId)
      */
     void onFolderStateSet(BookmarkId folder);
+
+    /**
+     * Called when the UI state is set to {@link BookmarkUIState#STATE_SEARCHING}.
+     */
+    void onSearchStateSet();
 }