Clear an extension's filtered events when a context is destroyed.

extensions/common/value_counter.h

 // Copyright 2014 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 EXTENSIONS_COMMON_VALUE_COUNTER_H_
 #define EXTENSIONS_COMMON_VALUE_COUNTER_H_
 
-#include <vector>
-
-#include "base/memory/linked_ptr.h"
+#include "base/memory/scoped_vector.h"
 
 namespace base {
 class Value;
 }
 
 namespace extensions {
 
-// Keeps a running count of Values, like map<Value, int>. Adding / removing
-// values increments / decrements the count associated with a given Value.
+// Keeps a running count of Values, like map<Value, int>. Adding/removing
+// values increments/decrements the count associated with a given Value.
 //
 // Add() and Remove() are linear in the number of Values in the ValueCounter,
 // because there is no operator<() defined on Value, so we must iterate to find
 // whether a Value is equal to an existing one.
 class ValueCounter {
  public:
   ValueCounter();
   ~ValueCounter();
 
-  // Adds |value| to the set and returns how many equal values are in the set
-  // after. Does not take ownership of |value|. In the case where a Value equal
-  // to |value| doesn't already exist in this map, this function makes a
-  // DeepCopy() of |value|.
-  int Add(const base::Value& value);
+  // Adds |value| to the set. In the case where a Value equal to |value|
+  // doesn't already exist in this map, this function makes a copy of |value|
+  // and returns true. Otherwise, it returns false.
+  bool Add(const base::Value& value);
 
-  // Removes |value| from the set and returns how many equal values are in
-  // the set after.
-  int Remove(const base::Value& value);
+  // Removes |value| from the set, and returns true if it removed the last
+  // value equal to |value|. If there are more equal values, or if there
+  // weren't any in the first place, returns false.
+  bool Remove(const base::Value& value);
 
-  // Same as Add() but only performs the add if the value isn't present.
-  int AddIfMissing(const base::Value& value);
+  // Returns true if there are no values of any type being counted.
+  bool is_empty() const { return entries_.empty(); }
 
  private:
-  class Entry {
-   public:
-    explicit Entry(const base::Value& value);
-    ~Entry();
-
-    int Increment();
-    int Decrement();
-
-    const base::Value* value() const { return value_.get(); }
-    int count() const { return count_; }
-
-   private:
-    linked_ptr<base::Value> value_;
-    int count_;
-
-    DISALLOW_COPY_AND_ASSIGN(Entry);
-  };
-  typedef std::vector<linked_ptr<Entry> > EntryList;
-
-  int AddImpl(const base::Value& value, bool increment);
-
-  EntryList entries_;
+  struct Entry;
+  ScopedVector<Entry> entries_;
 
   DISALLOW_COPY_AND_ASSIGN(ValueCounter);
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_COMMON_VALUE_COUNTER_H_