Remove EmptyRuleIterators with nullptrs.

components/content_settings/core/browser/content_settings_rule.h

 // Copyright (c) 2011 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.
 
 // Interface for objects providing content setting rules.
 
 #ifndef COMPONENTS_CONTENT_SETTINGS_CORE_BROWSER_CONTENT_SETTINGS_RULE_H_
 #define COMPONENTS_CONTENT_SETTINGS_CORE_BROWSER_CONTENT_SETTINGS_RULE_H_
 
 #include <memory>
@@ skipping 21 matching lines @@
   linked_ptr<base::Value> value;
 };
 
 class RuleIterator {
  public:
   virtual ~RuleIterator();
   virtual bool HasNext() const = 0;
   virtual Rule Next() = 0;
 };
 
-class EmptyRuleIterator : public RuleIterator {
- public:
-  ~EmptyRuleIterator() override;
-  bool HasNext() const override;
-  Rule Next() override;
-};
-
 class ConcatenationIterator : public RuleIterator {
  public:
   // ConcatenationIterator takes ownership of the pointers in the |iterators|
   // list and |auto_lock|. |auto_lock| can be NULL if no locking is needed.
   ConcatenationIterator(std::vector<std::unique_ptr<RuleIterator>> iterators,
                         base::AutoLock* auto_lock);
   ~ConcatenationIterator() override;
   bool HasNext() const override;
   Rule Next() override;
 
  private:
   std::vector<std::unique_ptr<RuleIterator>> iterators_;
   std::unique_ptr<base::AutoLock> auto_lock_;
 };
 
 }  // namespace content_settings
 
 #endif  // COMPONENTS_CONTENT_SETTINGS_CORE_BROWSER_CONTENT_SETTINGS_RULE_H_