Remove redundant field initialization in Java code.

chrome/android/java/src/org/chromium/chrome/browser/media/ui/MediaSessionTabHelper.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.ui;
 
 import android.app.Activity;
 import android.content.Intent;
 import android.graphics.Bitmap;
 import android.media.AudioManager;
@@ skipping 28 matching lines @@
  * media actions from the controls to the {@link org.chromium.content.browser.MediaSession}
  */
 public class MediaSessionTabHelper implements MediaImageCallback {
     private static final String TAG = "MediaSession";
 
     private static final String UNICODE_PLAY_CHARACTER = "\u25B6";
     private static final int MINIMAL_FAVICON_SIZE = 114;
     private static final int HIDE_NOTIFICATION_DELAY_MILLIS = 1000;
 
     private Tab mTab;
-    private Bitmap mPageMediaImage = null;
-    private Bitmap mFavicon = null;
-    private Bitmap mCurrentMediaImage = null;
-    private String mOrigin = null;
+    private Bitmap mPageMediaImage;
+    private Bitmap mFavicon;
+    private Bitmap mCurrentMediaImage;
+    private String mOrigin;
     private MediaSessionObserver mMediaSessionObserver;
     private int mPreviousVolumeControlStream = AudioManager.USE_DEFAULT_STREAM_TYPE;
-    private MediaNotificationInfo.Builder mNotificationInfoBuilder = null;
+    private MediaNotificationInfo.Builder mNotificationInfoBuilder;
     // The fallback title if |mPageMetadata| is null or its title is empty.
-    private String mFallbackTitle = null;
+    private String mFallbackTitle;
     // The metadata set by the page.
-    private MediaMetadata mPageMetadata = null;
+    private MediaMetadata mPageMetadata;
     // The currently showing metadata.
-    private MediaMetadata mCurrentMetadata = null;
-    private MediaImageManager mMediaImageManager = null;
-    private Set<Integer> mMediaSessionActions = null;
+    private MediaMetadata mCurrentMetadata;
+    private MediaImageManager mMediaImageManager;
+    private Set<Integer> mMediaSessionActions;
     private Handler mHandler;
     // The delayed task to hide notification. Hiding notification can be immediate or delayed.
     // Delayed hiding will schedule this delayed task to |mHandler|. The task will be canceled when
     // showing or immediate hiding.
     private Runnable mHideNotificationDelayedTask;
 
     @VisibleForTesting
     @Nullable
     MediaSessionObserver getMediaSessionObserverForTesting() {
         return mMediaSessionObserver;
@@ skipping 394 matching lines @@
     }
 
     private Bitmap getNotificationImage() {
         return (mPageMediaImage != null) ? mPageMediaImage : mFavicon;
     }
 
     private boolean isNotificationHiddingOrHidden() {
         return mNotificationInfoBuilder == null;
     }
 }