Remove unnecessary public functions

contracts/exchange-libs/contracts/src/LibEIP712ExchangeDomain.sol

@@ -24,10 +24,10 @@ import "@0x/contracts-utils/contracts/src/LibEIP712.sol";
 contract LibEIP712ExchangeDomain {
 
     // EIP712 Exchange Domain Name value
-    string constant public EIP712_EXCHANGE_DOMAIN_NAME = "0x Protocol";
+    string constant internal _EIP712_EXCHANGE_DOMAIN_NAME = "0x Protocol";
 
     // EIP712 Exchange Domain Version value
-    string constant public EIP712_EXCHANGE_DOMAIN_VERSION = "3.0.0";
+    string constant internal _EIP712_EXCHANGE_DOMAIN_VERSION = "3.0.0";
 
     // Hash of the EIP712 Domain Separator data
     // solhint-disable-next-line var-name-mixedcase
@@ -43,8 +43,8 @@ contract LibEIP712ExchangeDomain {
     {
         address verifyingContractAddress = verifyingContractAddressIfExists == address(0) ? address(this) : verifyingContractAddressIfExists;
         EIP712_EXCHANGE_DOMAIN_HASH = LibEIP712.hashEIP712Domain(
-            EIP712_EXCHANGE_DOMAIN_NAME,
-            EIP712_EXCHANGE_DOMAIN_VERSION,
+            _EIP712_EXCHANGE_DOMAIN_NAME,
+            _EIP712_EXCHANGE_DOMAIN_VERSION,
             chainId,
             verifyingContractAddress
         );

contracts/exchange-libs/contracts/src/LibMathRichErrors.sol

@@ -7,10 +7,6 @@ library LibMathRichErrors {
     bytes internal constant DIVISION_BY_ZERO_ERROR =
         hex"a791837c";
 
-    // bytes4(keccak256("DivisionByZeroError()"))
-    bytes4 internal constant DIVISION_BY_ZERO_ERROR_SELECTOR =
-        0xa791837c;
-
     // bytes4(keccak256("RoundingError(uint256,uint256,uint256)"))
     bytes4 internal constant ROUNDING_ERROR_SELECTOR =
         0x339f3de2;

contracts/exchange/contracts/src/Exchange.sol

@@ -35,8 +35,6 @@ contract Exchange is
     MixinWrapperFunctions,
     MixinTransferSimulator
 {
-    string constant public VERSION = "3.0.0";
-
     /// @dev Mixins are instantiated in the order they are inherited
     /// @param chainId Chain ID of the network this contract is deployed on.
     constructor (uint256 chainId)

contracts/exchange/contracts/src/MixinExchangeCore.sol

@@ -369,7 +369,7 @@ contract MixinExchangeCore is
         // regular validation.
         address makerAddress = order.makerAddress;
         if (orderInfo.orderTakerAssetFilledAmount == 0 ||
-            doesSignatureRequireRegularValidation(
+            _doesSignatureRequireRegularValidation(
                 orderInfo.orderHash,
                 makerAddress,
                 signature

contracts/exchange/contracts/src/MixinSignatureValidator.sol

@@ -177,12 +177,12 @@ contract MixinSignatureValidator is
     /// @param signature The signature for `hash`.
     /// @return needsRegularValidation True if the signature should be validated
     ///                                for every action.
-    function doesSignatureRequireRegularValidation(
+    function _doesSignatureRequireRegularValidation(
         bytes32 hash,
         address signerAddress,
         bytes memory signature
     )
-        public
+        internal
         pure
         returns (bool needsRegularValidation)
     {
@@ -195,6 +195,7 @@ contract MixinSignatureValidator is
             signatureType == SignatureType.Wallet ||
             signatureType == SignatureType.Validator ||
             signatureType == SignatureType.EIP1271Wallet;
+        return needsRegularValidation;
     }
 
     /// @dev Verifies that an order, with provided order hash, has been signed

contracts/exchange/contracts/src/interfaces/IExchange.sol

@@ -20,6 +20,7 @@ pragma solidity ^0.5.9;
 pragma experimental ABIEncoderV2;
 
 import "./IExchangeCore.sol";
+import "./IProtocolFees.sol";
 import "./IMatchOrders.sol";
 import "./ISignatureValidator.sol";
 import "./ITransactions.sol";
@@ -30,6 +31,7 @@ import "./ITransferSimulator.sol";
 
 // solhint-disable no-empty-blocks
 contract IExchange is
+    IProtocolFees,
     IExchangeCore,
     IMatchOrders,
     ISignatureValidator,

contracts/exchange/contracts/src/interfaces/IProtocolFees.sol

@@ -21,9 +21,6 @@ pragma solidity ^0.5.9;
 
 contract IProtocolFees {
 
-    // The proxy id of the weth asset proxy.
-    bytes internal constant WETH_ASSET_DATA = hex"f47261b0";
-
     // Logs updates to the protocol fee multiplier.
     event ProtocolFeeMultiplier(uint256 oldProtocolFeeMultiplier, uint256 updatedProtocolFeeMultiplier);
 

contracts/exchange/contracts/src/interfaces/ISignatureValidator.sol

@@ -98,21 +98,6 @@ contract ISignatureValidator {
         view
         returns (bool isValid);
 
-    /// @dev Checks if a signature is of a type that should be verified for
-    /// every subsequent fill.
-    /// @param hash The hash of the order/transaction.
-    /// @param signature The signature for `hash`.
-    /// @return needsRegularValidation True if the signature should be validated
-    ///                                for every operation.
-    function doesSignatureRequireRegularValidation(
-        bytes32 hash,
-        address signerAddress,
-        bytes memory signature
-    )
-        public
-        pure
-        returns (bool needsRegularValidation);
-
     /// @dev Verifies that an order, with provided order hash, has been signed
     ///      by the given signer.
     /// @param order The order.