Add WebCodecs full cycle test using realtime `latencyMode` (#41431)

diff --git a/webcodecs/full-cycle-test.https.any.js b/webcodecs/full-cycle-test.https.any.js
index 56671e6..d2e4ad9 100644
--- a/webcodecs/full-cycle-test.https.any.js
+++ b/webcodecs/full-cycle-test.https.any.js
@@ -68,6 +68,9 @@
 
 async function runFullCycleTest(t, options) {
   let encoder_config = { ...ENCODER_CONFIG };
+  if (options.realTimeLatencyMode) {
+    encoder_config.latencyMode = 'realtime';
+  }
   let encoder_color_space = {};
   const w = encoder_config.width;
   const h = encoder_config.height;
@@ -162,6 +165,10 @@
 }, 'Encoding and decoding cycle');
 
 promise_test(async t => {
+  return runFullCycleTest(t, {realTimeLatencyMode: true});
+}, 'Encoding and decoding cycle with realtime latency mode');
+
+promise_test(async t => {
   if (ENCODER_CONFIG.hasEmbeddedColorSpace)
     return runFullCycleTest(t, {stripDecoderConfigColorSpace: true});
 }, 'Encoding and decoding cycle w/ stripped color space');