hotkeys.js: add 'c' for transcript

youtube/static/js/common.js

@@ -0,0 +1,23 @@
+Q = document.querySelector.bind(document);
+function text(msg) { return document.createTextNode(msg); }
+function clearNode(node) { while (node.firstChild) node.removeChild(node.firstChild); }
+function toMS(s) {
+  var s = Math.floor(s);
+  var m = Math.floor(s/60); var s = s % 60;
+  return `0${m}:`.slice(-3) + `0${s}`.slice(-2);
+}
+
+
+var cur_tt_idx = 0;
+function getActiveTranscriptTrackIdx() {
+    let tts = Q("video").textTracks;
+    if (!tts.length) return;
+    for (let i=0; i < tts.length; i++) {
+        if (tts[i].mode == "showing") {
+            cur_tt_idx = i;
+            return cur_tt_idx;
+        }
+    }
+    return cur_tt_idx;
+}
+function getActiveTranscriptTrack() { return Q("video").textTracks[getActiveTranscriptTrackIdx()]; }