Make mpd parser more ameanable for extension.

library/src/main/java/com/google/android/exoplayer/dash/mpd/AdaptationSet.java

@@ -21,7 +21,7 @@ import java.util.List;
 /**
  * Represents a set of interchangeable encoded versions of a media content component.
  */
-public final class AdaptationSet {
+public class AdaptationSet {
 
   public static final int TYPE_UNKNOWN = -1;
   public static final int TYPE_VIDEO = 0;

library/src/main/java/com/google/android/exoplayer/dash/mpd/ContentProtection.java

@@ -15,36 +15,21 @@
  */
 package com.google.android.exoplayer.dash.mpd;
 
-import java.util.Collections;
-import java.util.Map;
-
 /**
- * Represents a ContentProtection tag in an AdaptationSet. Holds arbitrary data for various DRM
- * schemes.
+ * Represents a ContentProtection tag in an AdaptationSet.
  */
-public final class ContentProtection {
+public class ContentProtection {
 
   /**
    * Identifies the content protection scheme.
    */
   public final String schemeUriId;
-  /**
-   * Protection scheme specific data.
-   */
-  public final Map<String, String> keyedData;
 
   /**
    * @param schemeUriId Identifies the content protection scheme.
-   * @param keyedData Data specific to the scheme.
    */
-  public ContentProtection(String schemeUriId, Map<String, String> keyedData) {
+  public ContentProtection(String schemeUriId) {
     this.schemeUriId = schemeUriId;
-    if (keyedData != null) {
-      this.keyedData = Collections.unmodifiableMap(keyedData);
-    } else {
-      this.keyedData = Collections.emptyMap();
-    }
-
   }
 
 }

library/src/main/java/com/google/android/exoplayer/dash/mpd/MediaPresentationDescription.java

@@ -21,7 +21,7 @@ import java.util.List;
 /**
  * Represents a DASH media presentation description (mpd).
  */
-public final class MediaPresentationDescription {
+public class MediaPresentationDescription {
 
   public final long availabilityStartTime;
 

library/src/main/java/com/google/android/exoplayer/dash/mpd/Period.java

@@ -21,7 +21,7 @@ import java.util.List;
 /**
  * Encapsulates media content components over a contiguous period of time.
  */
-public final class Period {
+public class Period {
 
   /**
    * The period identifier, if one exists.