Remove redundant field initialization in Java code.

printing/android/java/src/org/chromium/printing/PrintDocumentAdapterWrapper.java

 // Copyright 2013 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.printing;
 
 import android.annotation.TargetApi;
 import android.os.Build;
 import android.os.Bundle;
 import android.os.CancellationSignal;
@@ skipping 38 matching lines @@
         void onLayoutCancelled();
     }
 
     public static interface WriteResultCallbackWrapper {
         void onWriteFinished(PageRange[] pages);
         void onWriteFailed(CharSequence error);
         void onWriteCancelled();
     }
 
     public static class LayoutResultCallbackWrapperImpl implements LayoutResultCallbackWrapper {
-        private LayoutResultCallback mCallback = null;
+        private LayoutResultCallback mCallback;
         public LayoutResultCallbackWrapperImpl(LayoutResultCallback callback) {
             assert callback != null;
             mCallback = callback;
         }
 
         @Override
         public void onLayoutFinished(PrintDocumentInfo info, boolean changed) {
             mCallback.onLayoutFinished(info, changed);
         }
 
         @Override
         public void onLayoutFailed(CharSequence error) {
             mCallback.onLayoutFailed(error);
         }
 
         @Override
         public void onLayoutCancelled() {
             mCallback.onLayoutCancelled();
         }
     }
 
     public static class WriteResultCallbackWrapperImpl implements WriteResultCallbackWrapper {
-        private WriteResultCallback mCallback = null;
+        private WriteResultCallback mCallback;
         public WriteResultCallbackWrapperImpl(WriteResultCallback callback) {
             assert callback != null;
             mCallback = callback;
         }
 
         @Override
         public void onWriteFinished(PageRange[] pages) {
             mCallback.onWriteFinished(pages);
         }
 
@@ skipping 44 matching lines @@
         mPdfGenerator.onWrite(ranges, destination, cancellationSignal,
                 new WriteResultCallbackWrapperImpl(callback));
     }
 
     @Override
     public void onFinish() {
         super.onFinish();
         mPdfGenerator.onFinish();
     }
 }