Fix/doris 2701 webOS 5 startup improvements (unwanted seek)

[grabofus]

This PR will...

Fix issues on webOS 5 where an unnecessary seek is performed during startup if the manifest is updated while the first segment is being buffered.

video-dev#6998

Video demonstrating the issue where synchronizeToLiveEdge is triggered as soon as the first segment start getting inserted into the source buffer, but the currentTime is not yet adjusted to start position.

issue_3.mp4

[robwalch]

Would getLoadPosition work here?

    const currentTime = this.getLoadPosition();

[grabofus]

We might be able to, but we'd need to modify getLoadPosition() to check for media.currentTime as well, not sure if that'd have any impact on the rest of the code.

  protected getLoadPosition(): number {
    const { media } = this;
    // if we have not yet loaded any fragment, start loading from start position
    let pos = 0;
-   if (this.loadedmetadata && media) {
+   if (this.loadedmetadata && media && media.currentTime > 0) {
      pos = media.currentTime;
    } else if (this.nextLoadPosition) {
      pos = this.nextLoadPosition;
    }

    return pos;
  }

[robwalch]

I don't think so. getLoadPosition should return the position that should be buffered at any given time. If it determines that it should return media.currentTime and that has a value of 0 then that is the value that should be used, not startPosition or nextLoadPosition.

[grabofus]

ah okay, I'll give it a try 👍