Add some missing Javadoc from the drm package

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=128085240

library/src/main/java/com/google/android/exoplayer2/drm/DrmInitData.java

@@ -38,10 +38,16 @@ public final class DrmInitData implements Comparator<SchemeData>, Parcelable {
   // Lazily initialized hashcode.
   // Lazily initialized hashcode.
   private int hashCode;
   private int hashCode;
 
 
+  /**
+   * @param schemeDatas Scheme initialization data for possibly multiple DRM schemes.
+   */
   public DrmInitData(List<SchemeData> schemeDatas) {
   public DrmInitData(List<SchemeData> schemeDatas) {
     this(false, schemeDatas.toArray(new SchemeData[schemeDatas.size()]));
     this(false, schemeDatas.toArray(new SchemeData[schemeDatas.size()]));
   }
   }
 
 
+  /**
+   * @param schemeDatas Scheme initialization data for possibly multiple DRM schemes.
+   */
   public DrmInitData(SchemeData... schemeDatas) {
   public DrmInitData(SchemeData... schemeDatas) {
     this(true, schemeDatas);
     this(true, schemeDatas);
   }
   }

library/src/main/java/com/google/android/exoplayer2/drm/UnsupportedDrmException.java

@@ -30,12 +30,22 @@ public final class UnsupportedDrmException extends Exception {
    */
    */
   public static final int REASON_INSTANTIATION_ERROR = 2;
   public static final int REASON_INSTANTIATION_ERROR = 2;
 
 
+  /**
+   * {@link #REASON_UNSUPPORTED_SCHEME} or {@link #REASON_INSTANTIATION_ERROR}.
+   */
   public final int reason;
   public final int reason;
 
 
+  /**
+   * @param reason {@link #REASON_UNSUPPORTED_SCHEME} or {@link #REASON_INSTANTIATION_ERROR}.
+   */
   public UnsupportedDrmException(int reason) {
   public UnsupportedDrmException(int reason) {
     this.reason = reason;
     this.reason = reason;
   }
   }
 
 
+  /**
+   * @param reason {@link #REASON_UNSUPPORTED_SCHEME} or {@link #REASON_INSTANTIATION_ERROR}.
+   * @param cause The cause of this exception.
+   */
   public UnsupportedDrmException(int reason, Exception cause) {
   public UnsupportedDrmException(int reason, Exception cause) {
     super(cause);
     super(cause);
     this.reason = reason;
     this.reason = reason;