Fix android_webview FindBugs warnings revealed by N sdk

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

Index: android_webview/glue/java/src/com/android/webview/chromium/WebHistoryItemChromium.java
diff --git a/android_webview/glue/java/src/com/android/webview/chromium/WebHistoryItemChromium.java b/android_webview/glue/java/src/com/android/webview/chromium/WebHistoryItemChromium.java
index 5a93abc9c4f0a9e203b64270c34e1ff5fdcc20cf..d492bdff3a64a560f8a5f138de1b4fb21a4ffe30 100644
--- a/android_webview/glue/java/src/com/android/webview/chromium/WebHistoryItemChromium.java
+++ b/android_webview/glue/java/src/com/android/webview/chromium/WebHistoryItemChromium.java
@@ -82,7 +82,8 @@ public class WebHistoryItemChromium extends WebHistoryItem {
      */
     @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);