Hls NAME parsing changes

-   NAME is optionial now in the Hls Manifest
-   Use the id field in Format to store the NAME instead of
    a field in Variant to mimic DASH's behaviour
    (see the DASH Id PR, which is not merged yet at this time).

library/src/main/java/com/google/android/exoplayer/hls/HlsPlaylistParser.java

@@ -166,7 +166,7 @@ public final class HlsPlaylistParser implements UriLoadable.Parser<HlsPlaylist>
       } else if (line.startsWith(STREAM_INF_TAG)) {
         bitrate = HlsParserUtil.parseIntAttr(line, BANDWIDTH_ATTR_REGEX, BANDWIDTH_ATTR);
         codecs = HlsParserUtil.parseOptionalStringAttr(line, CODECS_ATTR_REGEX);
-        name = HlsParserUtil.parseStringAttr(line, NAME_ATTR_REGEX, NAME_ATTR);
+        name = HlsParserUtil.parseOptionalStringAttr(line, NAME_ATTR_REGEX);
         String resolutionString = HlsParserUtil.parseOptionalStringAttr(line,
             RESOLUTION_ATTR_REGEX);
         if (resolutionString != null) {

library/src/main/java/com/google/android/exoplayer/hls/Variant.java

@@ -26,13 +26,16 @@ public final class Variant implements FormatWrapper {
 
   public final String url;
   public final Format format;
-  public final String name;
 
   public Variant(int index, String name, String url, int bitrate, String codecs, int width, int height) {
     this.url = url;
-    this.name = name;
-    format = new Format(Integer.toString(index), MimeTypes.APPLICATION_M3U8, width, height, -1, -1,
-        -1, bitrate, null, codecs);
+    if (name != null) {
+      format = new Format(name, MimeTypes.APPLICATION_M3U8, width, height, -1, -1,
+              -1, bitrate, null, codecs);
+    } else {
+      format = new Format(Integer.toString(index), MimeTypes.APPLICATION_M3U8, width, height, -1, -1,
+              -1, bitrate, null, codecs);
+    }
   }
 
   @Override