Fix android_webview FindBugs warnings revealed by N sdk

android_webview/glue/java/src/com/android/webview/chromium/WebHistoryItemChromium.java

 // Copyright 2014 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 com.android.webview.chromium;
 
 import android.graphics.Bitmap;
 import android.webkit.WebHistoryItem;
 
 import org.chromium.base.annotations.SuppressFBWarnings;
@@ skipping 64 matching lines @@
         mOriginalUrl = originalUrl;
         mTitle = title;
         mFavicon = favicon;
     }
 
     /**
      * See {@link android.webkit.WebHistoryItem#clone}.
      */
     @SuppressFBWarnings({
             "CHROMIUM_SYNCHRONIZED_METHOD",
-            "CN_IDIOM_NO_SUPER_CALL"})
+            "CN_IDIOM_NO_SUPER_CALL",
+            "CN_IMPLEMENTS_CLONE_BUT_NOT_CLONEABLE"})
     @Override
     public synchronized WebHistoryItemChromium clone() {
         return new WebHistoryItemChromium(mUrl, mOriginalUrl, mTitle, mFavicon);
     }
 }