[string] Refactor direct string conversions

src/builtins/builtins-regexp.h

Index: src/builtins/builtins-regexp.h
diff --git a/src/builtins/builtins-regexp.h b/src/builtins/builtins-regexp.h
index b41d58786512ece32168c08268d08ed60cc0f750..97e5b0f307c68da75fb967bd80c7d7074afcabfe 100644
--- a/src/builtins/builtins-regexp.h
+++ b/src/builtins/builtins-regexp.h
@@ -37,7 +37,7 @@ class RegExpBuiltinsAssembler : public CodeStubAssembler {
   // offsets into the given {string}.
   void GetStringPointers(Node* const string, Node* const offset,
                          Node* const last_index, Node* const string_length,
-                         bool is_one_byte, Variable* var_string_start,
+                         String::Encoding encoding, Variable* var_string_start,
                          Variable* var_string_end);
 
   // Low level logic around the actual call into generated Irregexp code.