Optimize constructor of ERC777 (#2551)

(cherry picked from commit 62af16b9)

CHANGELOG.md

@@ -16,6 +16,7 @@
  * Overall reorganisation of the contract folder to improve clarity and discoverability. ([#2503](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2503))
  * `ERC20Capped`: optimize gas usage of by enforcing te check directly in `_mint`. ([#2524](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2524))
  * Rename `UpgradeableProxy` to `ERC1967Proxy`. ([#2547](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2547))
+ * `ERC777`: Optimize the gas costs of the constructor. ([#2551](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2551))
 
 ### How to upgrade from 3.x
 

contracts/token/ERC777/ERC777.sol

@@ -65,8 +65,8 @@ contract ERC777 is Context, IERC777, IERC20 {
         _symbol = symbol_;
 
         _defaultOperatorsArray = defaultOperators_;
-        for (uint256 i = 0; i < _defaultOperatorsArray.length; i++) {
-            _defaultOperators[_defaultOperatorsArray[i]] = true;
+        for (uint256 i = 0; i < defaultOperators_.length; i++) {
+            _defaultOperators[defaultOperators_[i]] = true;
         }
 
         // register interfaces