buffer-controller: don't concurrently append data in multiple sourceb…

…uffers

use this.appending boolean to ensure that one append is performed at a time
avoid missing notifications received in *stream-controller and fragLoopLoadingError/stuck stream controller

related to #30

src/controller/buffer-controller.js

@@ -135,7 +135,7 @@ class BufferController extends EventHandler {
     if (this._needsEos) {
       this.onBufferEos();
     }
-
+    this.appending = false;
     this.hls.trigger(Event.BUFFER_APPENDED, { parent : this.parent});
 
     this.doAppending();
@@ -282,11 +282,9 @@ class BufferController extends EventHandler {
         logger.error('trying to append although a media error occured, flush segment and abort');
         return;
       }
-      for (var type in sourceBuffer) {
-        if (sourceBuffer[type].updating) {
-          //logger.log('sb update in progress');
-          return;
-        }
+      if (this.appending) {
+        //logger.log(`sb appending in progress`);
+        return;
       }
       if (segments && segments.length) {
         var segment = segments.shift();
@@ -297,6 +295,7 @@ class BufferController extends EventHandler {
             sourceBuffer[segment.type].appendBuffer(segment.data);
             this.appendError = 0;
             this.appended++;
+            this.appending = true;
           } else {
             // in case we don't have any source buffer matching with this segment type,
             // it means that Mediasource fails to create sourcebuffer