Make some private functions internal to allow the developpement of "withSignature" functions (like permit)

CHANGELOG.md

@@ -1,5 +1,10 @@
 # Changelog
 
+## Unreleased
+
+ * `Ownable`: add `_transferOwnership` to Ownable. ([#2568](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/#2568))
+ * `AccessControl`: make some private functions internal. ([#2568](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/#2568))
+
 ## 4.3.1
 
  * `TimelockController`: Add additional isOperationReady check.

contracts/access/AccessControl.sol

@@ -194,14 +194,14 @@ abstract contract AccessControl is Context, IAccessControl, ERC165 {
         emit RoleAdminChanged(role, previousAdminRole, adminRole);
     }
 
-    function _grantRole(bytes32 role, address account) private {
+    function _grantRole(bytes32 role, address account) internal virtual {
         if (!hasRole(role, account)) {
             _roles[role].members[account] = true;
             emit RoleGranted(role, account, _msgSender());
         }
     }
 
-    function _revokeRole(bytes32 role, address account) private {
+    function _revokeRole(bytes32 role, address account) internal virtual {
         if (hasRole(role, account)) {
             _roles[role].members[account] = false;
             emit RoleRevoked(role, account, _msgSender());

contracts/access/Ownable.sol

@@ -25,7 +25,7 @@ abstract contract Ownable is Context {
      * @dev Initializes the contract setting the deployer as the initial owner.
      */
     constructor() {
-        _setOwner(_msgSender());
+        _transferOwnership(_msgSender());
     }
 
     /**
@@ -51,7 +51,7 @@ abstract contract Ownable is Context {
      * thereby removing any functionality that is only available to the owner.
      */
     function renounceOwnership() public virtual onlyOwner {
-        _setOwner(address(0));
+        _transferOwnership(address(0));
     }
 
     /**
@@ -60,10 +60,14 @@ abstract contract Ownable is Context {
      */
     function transferOwnership(address newOwner) public virtual onlyOwner {
         require(newOwner != address(0), "Ownable: new owner is the zero address");
-        _setOwner(newOwner);
+        _transferOwnership(newOwner);
     }
 
-    function _setOwner(address newOwner) private {
+    /**
+     * @dev Internal function that forces an ownership change. Can be used to
+     * implement custom ownership management logic in childs contracts.
+     */
+    function _transferOwnership(address newOwner) internal virtual {
         address oldOwner = _owner;
         _owner = newOwner;
         emit OwnershipTransferred(oldOwner, newOwner);