feat(HLS): Improve Low Latency performance in HLS (shaka-project#4952)

In Low Latency HLS, the low latency segments are integer segments
instead of partial segments like in DASH, so we can avoid reading part
of the segment and increase performance on low-end devices.

lib/media/streaming_engine.js

@@ -1261,10 +1261,9 @@ shaka.media.StreamingEngine = class {
               stream.mimeType == 'audio/mp4';
       const isReadableStreamSupported = window.ReadableStream;
       // Enable MP4 low latency streaming with ReadableStream chunked data.
-      // Disabled when AES-128 is present, as we cannot decrypt part of a
-      // segment.
+      // And only for DASH.
       if (this.config_.lowLatencyMode && isReadableStreamSupported && isMP4 &&
-          !reference.hlsAes128Key) {
+          this.manifest_.type != shaka.media.ManifestParser.HLS) {
         let remaining = new Uint8Array(0);
         let processingResult = false;
         let callbackCalled = false;