close #8146 (#8152)

std/hl/Bytes.hx

@@ -174,8 +174,8 @@ package hl;
 		return null;
 	}
 
-	@:hlNative("std", "utf16_to_utf8")
-	public function utf16ToUtf8(bytePos:Int, outSize:Ref<Int>):Bytes {
+	@:hlNative("std","utf16_to_utf8")
+	public function utf16ToUtf8(len:Int, outSize:Ref<Int>) : Bytes {
 		return null;
 	}
 

std/hl/_std/haxe/io/Bytes.hx

@@ -221,7 +221,7 @@ class Bytes {
 				return new Bytes(s.bytes.sub(0, s.length << 1), s.length << 1);
 			case UTF8:
 				var size = 0;
-				var b = s.bytes.utf16ToUtf8(0, size);
+				var b = s.bytes.utf16ToUtf8(s.length, size);
 				return new Bytes(b, size);
 		}
 	}