Remove redundant field initialization in Java code.

media/capture/content/android/java/src/org/chromium/media/ScreenCapture.java

 // Copyright 2016 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.media;
 
 import android.annotation.TargetApi;
 import android.app.Activity;
 import android.app.Fragment;
 import android.app.FragmentManager;
@@ skipping 41 matching lines @@
 
     private static enum CaptureState { ATTACHED, ALLOWED, STARTED, STOPPING, STOPPED }
     private static enum DeviceOrientation { PORTRAIT, LANDSCAPE }
     private final Object mCaptureStateLock = new Object();
     private CaptureState mCaptureState = CaptureState.STOPPED;
 
     private MediaProjection mMediaProjection;
     private MediaProjectionManager mMediaProjectionManager;
     private VirtualDisplay mVirtualDisplay;
     private Surface mSurface;
-    private ImageReader mImageReader = null;
+    private ImageReader mImageReader;
     private HandlerThread mThread;
     private Handler mBackgroundHandler;
     private Display mDisplay;
     private DeviceOrientation mCurrentOrientation;
     private Intent mResultData;
 
     private int mScreenDensity;
     private int mWidth;
     private int mHeight;
     private int mFormat;
@@ skipping 348 matching lines @@
             long timestamp);
 
     // Method for ScreenCapture implementations to notify activity result.
     private native void nativeOnActivityResult(
             long nativeScreenCaptureMachineAndroid, boolean result);
 
     // Method for ScreenCapture implementations to notify orientation change.
     private native void nativeOnOrientationChange(
             long nativeScreenCaptureMachineAndroid, int rotation);
 }