Bug 1293613: Never attempt to read past end of manifest table. r=gerald

Should the events being waited for take a while to fire, we could have attempted to append more segments than the table contain causing an exception.

MozReview-Commit-ID: HnmLTqNQ5rb

--HG--
extra : rebase_source : f9b703a0ed1f3b950428dc55dd7943068bc6aa2d

testing/web-platform/tests/media-source/mediasource-util.js

@@ -305,7 +305,10 @@
                 return;
 
             i++;
-            MediaSourceUtil.append(test, sourceBuffer, MediaSourceUtil.extractSegmentData(mediaData, segmentInfo.media[i]), onAppendDone);
+            if (i < segmentInfo.media.length)
+            {
+                MediaSourceUtil.append(test, sourceBuffer, MediaSourceUtil.extractSegmentData(mediaData, segmentInfo.media[i]), onAppendDone);
+            }
         };
         MediaSourceUtil.append(test, sourceBuffer, MediaSourceUtil.extractSegmentData(mediaData, segmentInfo.media[i]), onAppendDone);