Remove redundant field initialization in Java code.

components/sync/android/java/src/org/chromium/components/sync/ModelTypeHelper.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.components.sync;
 
 import com.google.ipc.invalidation.external.client.types.ObjectId;
 import com.google.protos.ipc.invalidation.Types;
 
 import org.chromium.base.VisibleForTesting;
@@ skipping 18 matching lines @@
      * {@link ModelTypeHelper#toNotificationType()} for tests.
      */
     public interface TestDelegate { public String toNotificationType(int modelType); }
 
     private static final String TAG = "ModelTypeHelper";
 
     private static final Object sLock = new Object();
 
     private static final int[] NON_INVALIDATION_TYPES_ARRAY = new int[] {ModelType.PROXY_TABS};
 
-    private static TestDelegate sDelegate = null;
+    private static TestDelegate sDelegate;
 
     // Convenience sets for checking whether a type can have invalidations. Some ModelTypes
     // such as PROXY_TABS are not real types and can't be registered. Initializing these
     // once reduces toNotificationType() calls in the isInvalidationType() method.
-    private static Set<String> sNonInvalidationTypes = null;
+    private static Set<String> sNonInvalidationTypes;
 
     /**
      * Initializes the non-invalidation sets. Called lazily the first time they're needed.
      */
     private static void initNonInvalidationTypes() {
         synchronized (sLock) {
             if (sNonInvalidationTypes != null) return;
 
             sNonInvalidationTypes = new HashSet<String>();
             for (int i = 0; i < NON_INVALIDATION_TYPES_ARRAY.length; i++) {
@@ skipping 63 matching lines @@
         return objectIds;
     }
 
     @VisibleForTesting
     public static void setTestDelegate(TestDelegate delegate) {
         sDelegate = delegate;
     }
 
     private static native String nativeModelTypeToNotificationType(int modelType);
 }