Add scoped_ptr-safe base::Value to Dictionary/List conversion functions.

base/values.h

 // Copyright (c) 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.
 
 // This file specifies a recursive data storage class called Value intended for
 // storing settings and other persistable data.
 //
 // A Value represents something that can be stored in JSON or passed to/from
 // JavaScript. As such, it is NOT a generalized variant type, since only the
 // types supported by JavaScript/JSON are supported.
@@ skipping 191 matching lines @@
   size_t size_;
 
   DISALLOW_COPY_AND_ASSIGN(BinaryValue);
 };
 
 // DictionaryValue provides a key-value dictionary with (optional) "path"
 // parsing for recursive access; see the comment at the top of the file. Keys
 // are |std::string|s and should be UTF-8 encoded.
 class BASE_EXPORT DictionaryValue : public Value {
  public:
+  // Returns |value| if it is a dictionary, nullptr otherwise.
+  static scoped_ptr<DictionaryValue> From(scoped_ptr<Value> value);
+
   DictionaryValue();
   ~DictionaryValue() override;
 
   // Overridden from Value:
   bool GetAsDictionary(DictionaryValue** out_value) override;
   bool GetAsDictionary(const DictionaryValue** out_value) const override;
 
   // Returns true if the current dictionary has a value for the given key.
   bool HasKey(const std::string& key) const;
 
@@ skipping 158 matching lines @@
 
   DISALLOW_COPY_AND_ASSIGN(DictionaryValue);
 };
 
 // This type of Value represents a list of other Value values.
 class BASE_EXPORT ListValue : public Value {
  public:
   typedef ValueVector::iterator iterator;
   typedef ValueVector::const_iterator const_iterator;
 
+  // Returns |value| if it is a list, nullptr otherwise.
+  static scoped_ptr<ListValue> From(scoped_ptr<Value> value);
+
   ListValue();
   ~ListValue() override;
 
   // Clears the contents of this ListValue
   void Clear();
 
   // Returns the number of Values in this list.
   size_t GetSize() const { return list_.size(); }
 
   // Returns whether the list is empty.
@@ skipping 150 matching lines @@
 }
 
 BASE_EXPORT inline std::ostream& operator<<(std::ostream& out,
                                             const ListValue& value) {
   return out << static_cast<const Value&>(value);
 }
 
 }  // namespace base
 
 #endif  // BASE_VALUES_H_