Introduce Value::GetList and Value(ListStorage)

base/values.h

Index: base/values.h
diff --git a/base/values.h b/base/values.h
index 075bc9fbb8fed7cd14095f1de4daa8a3ab9c13ea..8d342a98b1fe96a111e16b468708e67d34bd3b2e 100644
--- a/base/values.h
+++ b/base/values.h
@@ -97,6 +97,9 @@ class BASE_EXPORT Value {
 
   explicit Value(DictStorage&& in_dict) noexcept;
 
+  explicit Value(const ListStorage& in_list);
+  explicit Value(ListStorage&& in_list) noexcept;
+
   Value& operator=(const Value& that);
   Value& operator=(Value&& that) noexcept;
 
@@ -130,6 +133,9 @@ class BASE_EXPORT Value {
   const std::string& GetString() const;
   const std::vector<char>& GetBlob() const;
 
+  ListStorage& GetList();
+  const ListStorage& GetList() const;
+
   size_t GetSize() const;         // DEPRECATED, use GetBlob().size() instead.
   const char* GetBuffer() const;  // DEPRECATED, use GetBlob().data() instead.