Remove redundant field initialization in Java code.

chrome/android/java/src/org/chromium/chrome/browser/physicalweb/UrlManager.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.physicalweb;
 
 import android.app.AlarmManager;
 import android.app.Notification;
 import android.app.NotificationManager;
 import android.app.PendingIntent;
@@ skipping 56 matching lines @@
     private static final String PREFS_VERSION_KEY = "physicalweb_version";
     private static final String PREFS_ALL_URLS_KEY = "physicalweb_all_urls";
     private static final String PREFS_NEARBY_URLS_KEY = "physicalweb_nearby_urls";
     private static final String PREFS_PWS_RESULTS_KEY = "physicalweb_pws_results";
     private static final String PREFS_NOTIFICATION_UPDATE_TIMESTAMP =
             "physicalweb_notification_update_timestamp";
     private static final int PREFS_VERSION = 4;
     private static final long STALE_NOTIFICATION_TIMEOUT_MILLIS = 30 * 60 * 1000;  // 30 Minutes
     private static final long MAX_CACHE_TIME = 24 * 60 * 60 * 1000;  // 1 Day
     private static final int MAX_CACHE_SIZE = 100;
-    private static UrlManager sInstance = null;
+    private static UrlManager sInstance;
     private final Context mContext;
     private final ObserverList<Listener> mObservers;
     private final Set<String> mNearbyUrls;
     private final Map<String, UrlInfo> mUrlInfoMap;
     private final Map<String, PwsResult> mPwsResultMap;
     private final PriorityQueue<String> mUrlsSortedByTimestamp;
     private NotificationManagerProxy mNotificationManager;
     private PwsClient mPwsClient;
     private long mNativePhysicalWebDataSourceAndroid;
 
@@ skipping 742 matching lines @@
 
     private native long nativeInit();
     private native void nativeAppendMetadataItem(long nativePhysicalWebCollection,
             String requestUrl, double distanceEstimate, int scanTimestamp, String siteUrl,
             String iconUrl, String title, String description, String groupId);
     private native void nativeOnFound(long nativePhysicalWebDataSourceAndroid, String url);
     private native void nativeOnLost(long nativePhysicalWebDataSourceAndroid, String url);
     private native void nativeOnDistanceChanged(
             long nativePhysicalWebDataSourceAndroid, String url, double distanceChanged);
 }