Add a MIME type MPEG-DASH (mpd files)

Fixes #2677

RELNOTES=`net`: Added the `MediaType` constant for MPEG-DASH.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=272444649

Author: joankaradimov

android/guava/src/com/google/common/net/MediaType.java

@@ -536,6 +536,18 @@ private static MediaType addKnownType(MediaType mediaType) {
   /** <a href="http://goo.gl/XDQ1h2">Microsoft Word</a> documents. */
   public static final MediaType MICROSOFT_WORD = createConstant(APPLICATION_TYPE, "msword");
 
+  /**
+   * Media type for <a
+   * href="https://en.wikipedia.org/wiki/Dynamic_Adaptive_Streaming_over_HTTP">Dynamic Adaptive
+   * Streaming over HTTP (DASH)</a>. This is <a
+   * href="https://www.iana.org/assignments/media-types/application/dash+xml">registered</a> with
+   * the IANA.
+   *
+   * @since NEXT
+   */
+  public static final MediaType MEDIA_PRESENTATION_DESCRIPTION =
+      createConstant(APPLICATION_TYPE, "dash+xml");
+
   /**
    * WASM applications. For more information see <a href="https://webassembly.org/">the Web Assembly
    * overview</a>.

guava/src/com/google/common/net/MediaType.java

@@ -536,6 +536,18 @@ private static MediaType addKnownType(MediaType mediaType) {
   /** <a href="http://goo.gl/XDQ1h2">Microsoft Word</a> documents. */
   public static final MediaType MICROSOFT_WORD = createConstant(APPLICATION_TYPE, "msword");
 
+  /**
+   * Media type for <a
+   * href="https://en.wikipedia.org/wiki/Dynamic_Adaptive_Streaming_over_HTTP">Dynamic Adaptive
+   * Streaming over HTTP (DASH)</a>. This is <a
+   * href="https://www.iana.org/assignments/media-types/application/dash+xml">registered</a> with
+   * the IANA.
+   *
+   * @since NEXT
+   */
+  public static final MediaType MEDIA_PRESENTATION_DESCRIPTION =
+      createConstant(APPLICATION_TYPE, "dash+xml");
+
   /**
    * WASM applications. For more information see <a href="https://webassembly.org/">the Web Assembly
    * overview</a>.