Use base::flat_map for base::Value dictionary storage.

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 11 matching lines @@
 
 #include <iosfwd>
 #include <map>
 #include <memory>
 #include <string>
 #include <utility>
 #include <vector>
 
 #include "base/base_export.h"
 #include "base/compiler_specific.h"
+#include "base/containers/flat_map.h"
 #include "base/macros.h"
 #include "base/memory/manual_constructor.h"
 #include "base/strings/string16.h"
 #include "base/strings/string_piece.h"
 
 namespace base {
 
 class DictionaryValue;
 class ListValue;
 class Value;
 using BinaryValue = Value;
 
 // The Value class is the base class for Values. A Value can be instantiated
 // via the Create*Value() factory methods, or by directly creating instances of
 // the subclasses.
 //
 // See the file-level comment above for more information.
 class BASE_EXPORT Value {
  public:
-  using DictStorage = std::map<std::string, std::unique_ptr<Value>>;
+  using DictStorage = base::flat_map<std::string, std::unique_ptr<Value>>;
   using ListStorage = std::vector<std::unique_ptr<Value>>;
 
   enum class Type {
     NONE = 0,
     BOOLEAN,
     INTEGER,
     DOUBLE,
     STRING,
     BINARY,
     DICTIONARY,
@@ skipping 26 matching lines @@
   explicit Value(const char* in_string);
   explicit Value(const std::string& in_string);
   explicit Value(std::string&& in_string) noexcept;
   explicit Value(const char16* in_string);
   explicit Value(const string16& in_string);
   explicit Value(StringPiece in_string);
 
   explicit Value(const std::vector<char>& in_blob);
   explicit Value(std::vector<char>&& in_blob) noexcept;
 
+  explicit Value(DictStorage&& in_dict) noexcept;
+
   Value& operator=(const Value& that);
   Value& operator=(Value&& that) noexcept;
 
   ~Value();
 
   // Returns the name for a given |type|.
   static const char* GetTypeName(Type type);
 
   // Returns the type of the value stored by the current Value object.
   // Each type will be implemented by only one subclass of Value, so it's
@@ skipping 422 matching lines @@
   return out << static_cast<const Value&>(value);
 }
 
 // Stream operator so that enum class Types can be used in log statements.
 BASE_EXPORT std::ostream& operator<<(std::ostream& out,
                                      const Value::Type& type);
 
 }  // namespace base
 
 #endif  // BASE_VALUES_H_