[Enhanced Bookmark]Rewrite initialization logic

chrome/android/java/src/org/chromium/chrome/browser/enhancedbookmarks/EnhancedBookmarkFilter.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.enhancedbookmarks;
 
 /**
  * Possible filters for the enhanced bookmarks.
  */
 enum EnhancedBookmarkFilter {
-    OFFLINE_PAGES
+    OFFLINE_PAGES("OFFLINE_PAGES");
+
+    /**
+     * An {@link EnhancedBookmarkFilter} can be persisted in URLs. To ensure the
+     * URLs are consistent, values should remain the same even after the enums
+     * are renamed.
+     */
+    public final String value;
+
+    private EnhancedBookmarkFilter(String value) {
+        this.value = value;
+    }
 }