Fix start time in live streams.

Commit 5cb7204 broke the start time calculations for live streams.
We don't need to set the start time with non-0 play-range start
values since Playhead will clamp the start time anyway.

Issue #1069

Change-Id: I40915cc5ecd81085c55149e7267d5025745ddb47

lib/player.js

@@ -639,8 +639,7 @@ shaka.Player.prototype.load = function(manifestUri, opt_startTime,
     }
     // MediaSource is open, so create the Playhead, MediaSourceEngine, and
     // StreamingEngine.
-    var startTime = opt_startTime || this.config_.playRangeStart;
-    this.playhead_ = this.createPlayhead(startTime);
+    this.playhead_ = this.createPlayhead(opt_startTime);
     this.playheadObserver_ = this.createPlayheadObserver();
     this.mediaSourceEngine_ = this.createMediaSourceEngine();