Cleanup of Ownership directory

contracts/mocks/OwnableInterfaceId.sol

@@ -10,6 +10,6 @@ import "../ownership/Ownable.sol";
 contract OwnableInterfaceId {
     function getInterfaceId() public pure returns (bytes4) {
         Ownable i;
-        return i.owner.selector ^ i.isOwner.selector ^ i.renounceOwnership.selector ^ i.transferOwnership.selector;
+        return i.owner.selector ^ i.renounceOwnership.selector ^ i.transferOwnership.selector;
     }
 }

contracts/ownership/Ownable.sol

@@ -6,6 +6,9 @@ import "../GSN/Context.sol";
  * there is an account (an owner) that can be granted exclusive access to
  * specific functions.
  *
+ * By default, the owner account will be the one that deploys the contract. This
+ * can later be changed with {transferOwnership}.
+ *
  * This module is used through inheritance. It will make available the modifier
  * `onlyOwner`, which can be applied to your functions to restrict their use to
  * the owner.
@@ -35,17 +38,10 @@ contract Ownable is Context {
      * @dev Throws if called by any account other than the owner.
      */
     modifier onlyOwner() {
-        require(isOwner(), "Ownable: caller is not the owner");
+        require(_owner == _msgSender(), "Ownable: caller is not the owner");
         _;
     }
 
-    /**
-     * @dev Returns true if the caller is the current owner.
-     */
-    function isOwner() public view returns (bool) {
-        return _msgSender() == _owner;
-    }
-
     /**
      * @dev Leaves the contract without owner. It will not be possible to call
      * `onlyOwner` functions anymore. Can only be called by the current owner.

test/ownership/Ownable.behavior.js

@@ -10,12 +10,10 @@ function shouldBehaveLikeOwnable (owner, [other]) {
     });
 
     it('changes owner after transfer', async function () {
-      expect(await this.ownable.isOwner({ from: other })).to.equal(false);
       const receipt = await this.ownable.transferOwnership(other, { from: owner });
       expectEvent(receipt, 'OwnershipTransferred');
 
       expect(await this.ownable.owner()).to.equal(other);
-      expect(await this.ownable.isOwner({ from: other })).to.equal(true);
     });
 
     it('should prevent non-owners from transferring', async function () {