Remove redundant field initialization in Java code.

chrome/android/java/src/org/chromium/chrome/browser/media/router/MediaRouteControllerDialogManager.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.media.router;
 
 import android.content.Context;
 import android.content.DialogInterface;
 import android.os.Handler;
 import android.support.v4.app.DialogFragment;
@@ skipping 27 matching lines @@
         super(source, applicationContext, delegate);
         mMediaRouteId = mediaRouteId;
     }
 
     /**
      * Fragment implementation for MediaRouteControllerDialogManager.
      */
     public static class Fragment extends MediaRouteControllerDialogFragment {
         private final Handler mHandler = new Handler();
         private final SystemVisibilitySaver mVisibilitySaver = new SystemVisibilitySaver();
-        private BaseMediaRouteDialogManager mManager = null;
-        private MediaRouter.Callback mCallback = null;
+        private BaseMediaRouteDialogManager mManager;
+        private MediaRouter.Callback mCallback;
 
         public Fragment() {
             mHandler.post(new Runnable() {
                 @Override
                 public void run() {
                     Fragment.this.dismiss();
                 }
             });
         }
 
@@ skipping 34 matching lines @@
         if (selector == null) return null;
 
         androidMediaRouter().addCallback(selector, mCallback);
 
         fragment.show(fm, DIALOG_FRAGMENT_TAG);
         fm.executePendingTransactions();
 
         return fragment;
     }
 }