Make expired time tracking contingent on setupFirstPlay succeeding

Don't increment seekable until the live stream has started to play. This more closely matches Safari's behavior WRT live stream and seekable.

src/playlist-loader.js

@@ -94,6 +94,10 @@
 
       PlaylistLoader.prototype.init.call(this);
 
+      // a flag that disables "expired time"-tracking this setting has
+      // no effect when not playing a live stream
+      this.trackExpiredTime_ = false;
+
       if (!srcUrl) {
         throw new Error('A non-empty playlist URL is required');
       }
@@ -267,6 +271,12 @@
         loader.bandwidth = xhr.bandwidth;
       };
 
+      // In a live list, don't keep track of the expired time until
+      // HLS tells us that "first play" has commenced
+      loader.on('firstplay', function() {
+        this.trackExpiredTime_ = true;
+      });
+
       // live playlist staleness timeout
       loader.on('mediaupdatetimeout', function() {
         if (loader.state !== 'HAVE_METADATA') {
@@ -360,6 +370,14 @@
       return;
     }
 
+    // don't track expired time until this flag is truthy
+    if (!this.trackExpiredTime_) {
+      return;
+    }
+
+    // if the update was the result of a rendition switch do not
+    // attempt to calculate expired_ since media-sequences need not
+    // correlate between renditions/variants
     if (update.uri !== outdated.uri) {
       return;
     }

src/videojs-hls.js

@@ -430,6 +430,9 @@ videojs.HlsHandler.prototype.setupFirstPlay = function() {
       // at least HAVE_FUTURE_DATA
       this.tech_.readyState() >= 1) {
 
+    // trigger the playlist loader to start "expired time"-tracking
+    this.playlists.trigger('firstplay');
+
     // seek to the latest media position for live videos
     seekable = this.seekable();
     if (seekable.length) {