[Sync] Replacing NULL with nullptr in code and null in comments for components/sync/

components/sync/syncable/entry.h

 // Copyright 2012 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.
 
 #ifndef COMPONENTS_SYNC_SYNCABLE_ENTRY_H_
 #define COMPONENTS_SYNC_SYNCABLE_ENTRY_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 245 matching lines @@
   const EntryKernel GetKernelCopy() const { return *kernel_; }
 
   // Dumps all entry info into a DictionaryValue and returns it.
   // Transfers ownership of the DictionaryValue to the caller.
   base::DictionaryValue* ToValue(Cryptographer* cryptographer) const;
 
  protected:  // Don't allow creation on heap, except by sync API wrappers.
   void* operator new(size_t size) { return (::operator new)(size); }
 
   inline explicit Entry(BaseTransaction* trans)
-      : basetrans_(trans), kernel_(NULL) {}
+      : basetrans_(trans), kernel_(nullptr) {}
 
  protected:
   BaseTransaction* const basetrans_;
 
   EntryKernel* kernel_;
 
  private:
   friend class syncer::syncable::Directory;
   friend class syncer::ReadNode;
   friend std::ostream& operator<<(std::ostream& s, const Entry& e);
 
   DISALLOW_COPY_AND_ASSIGN(Entry);
 };
 
 std::ostream& operator<<(std::ostream& os, const Entry& entry);
 
 }  // namespace syncable
 }  // namespace syncer
 
 #endif  // COMPONENTS_SYNC_SYNCABLE_ENTRY_H_