Do not assign currentTime of video unless MetaData is available.

Fixes shaka-project#101
Required for Firefox's and IE's MediaElement implementations.

lib/player/stream_video_source.js

@@ -1110,7 +1110,13 @@ shaka.player.StreamVideoSource.prototype.startStreams_ = function(
   // Set the video's current time before starting the streams so that the
   // streams begin buffering at the stream start time.
   shaka.log.info('Starting each stream from', streamStartTime);
-  this.video.currentTime = streamStartTime;
+
+  if (this.video.readyState >= HTMLMediaElement.HAVE_METADATA) {
+    this.video.currentTime = streamStartTime;
+  } else {
+    this.video.addEventListener('loadedmetadata',
+        this.setInitialCurrentTime.bind(this, streamStartTime));
+  }
 
   // Start the streams.
   for (var type in this.streamsByType_) {
@@ -1135,6 +1141,18 @@ shaka.player.StreamVideoSource.prototype.startStreams_ = function(
   this.enableTextTrack(this.subsNeeded_);
 };
 
+/**
+ * Sets the currentTime of the video element.  This is deferred if metadata
+ * has not been loaded yet.
+ *
+ * @param {number} streamStartTime
+ * @private
+ */
+shaka.player.StreamVideoSource.prototype.setInitialCurrentTime = function(
+    streamStartTime) {
+  this.video.currentTime = streamStartTime;
+  this.video.removeEventListener('loadedmetadata', this.setInitialCurrentTime);
+};
 
 /**
  * Start streams hook. Called immediately before setting the video's duration