fix: ensure all timelineregionenter events are fired (#6713)

Fixes #6711

lib/player.js

@@ -1992,7 +1992,7 @@ shaka.Player = class extends shaka.util.FakeEventTarget {
     const setupPlayhead = (startTime) => {
       this.playhead_ = this.createPlayhead(startTime);
       this.playheadObservers_ =
-          this.createPlayheadObserversForMSE_(startTimeOfLoad);
+          this.createPlayheadObserversForMSE_(startTime);
 
       // We need to start the buffer management code near the end because it
       // will set the initial buffering state and that depends on other
@@ -2764,16 +2764,16 @@ shaka.Player = class extends shaka.util.FakeEventTarget {
    * Create the observers for MSE playback. These observers are responsible for
    * notifying the app and player of specific events during MSE playback.
    *
-   * @param {number} startTimeOfLoad
+   * @param {number} startTime
    * @return {!shaka.media.PlayheadObserverManager}
    * @private
    */
-  createPlayheadObserversForMSE_(startTimeOfLoad) {
+  createPlayheadObserversForMSE_(startTime) {
     goog.asserts.assert(this.manifest_, 'Must have manifest');
     goog.asserts.assert(this.regionTimeline_, 'Must have region timeline');
     goog.asserts.assert(this.video_, 'Must have video element');
 
-    const startsPastZero = this.isLive() || startTimeOfLoad > 0;
+    const startsPastZero = this.isLive() || startTime > 0;
 
     // Create the region observer. This will allow us to notify the app when we
     // move in and out of timeline regions.