Micro-optimize emscripten_set_main_loop_timing. NFC (emscripten-core#26253)

Author: sbc100

src/lib/libeventloop.js

@@ -339,7 +339,10 @@ LibraryJSEventLoop = {
         MainLoop.requestAnimationFrame(MainLoop.runner);
       };
       MainLoop.method = 'rAF';
-    } else if (mode == {{{ cDefs.EM_TIMING_SETIMMEDIATE}}}) {
+    } else {
+#if ASSERTIONS
+      assert(mode == {{{ cDefs.EM_TIMING_SETIMMEDIATE}}});
+#endif
       if (!MainLoop.setImmediate) {
         if (globalThis.setImmediate) {
           MainLoop.setImmediate = setImmediate;

test/codesize/test_codesize_hello_dylink_all.json

@@ -1,7 +1,7 @@
 {
-  "a.out.js": 244700,
+  "a.out.js": 244691,
   "a.out.nodebug.wasm": 577696,
-  "total": 822396,
+  "total": 822387,
   "sent": [
     "IMG_Init",
     "IMG_Load",