inflate speed opts for old v8

lib/zlib/inftrees.js

@@ -191,19 +191,18 @@ module.exports = function inflate_table(type, lens, lens_index, codes, table, ta
    */
 
   /* set up for code type */
-  switch (type) {
-    case CODES:
+  // poor man optimization - use if-else instead of switch,
+  // to avoid deopts in old v8
+  if (type === CODES) {
       base = extra = work;    /* dummy value--not used */
       end = 19;
-      break;
-    case LENS:
+  } else if (type === LENS) {
       base = lbase;
       base_index -= 257;
       extra = lext;
       extra_index -= 257;
       end = 256;
-      break;
-    default:            /* DISTS */
+  } else {                    /* DISTS */
       base = dbase;
       extra = dext;
       end = -1;
@@ -323,4 +322,4 @@ module.exports = function inflate_table(type, lens, lens_index, codes, table, ta
   //opts.table_index += used;
   opts.bits = root;
   return 0;
-};
+};