webm_parser: Add new enum values

For the new stereo mode, see https://github.com/google/spatial-media/blob/master/docs/spherical-video-v2-rfc.md#webm-matroska
For the new color primaries, see ISO/IEC 23001-8:2016

Change-Id: I92c2bb0fedc2b1895d893ad55095d29c811c0dcf

webm_parser/include/webm/dom_types.h

@@ -782,6 +782,17 @@ enum class Primaries : std::uint64_t {
    */
   kSmpteSt4281 = 10,
 
+  /**
+   Society of Motion Picture and Television Engineers RP 431-2 (a.k.a. DCI-P3).
+   */
+  kSmpteRp431 = 11,
+
+  /**
+   Society of Motion Picture and Television Engineers EG 432-1
+   (a.k.a. DCI-P3 D65).
+   */
+  kSmpteEg432 = 12,
+
   /**
    JEDEC P22 phosphors/EBU Tech. 3213-E (1975).
    */
@@ -1046,6 +1057,12 @@ enum class StereoMode : std::uint64_t {
    Both eyes are laced in one block, right eye is first.
    */
   kBlockLacedRightFirst = 14,
+
+  /**
+   Stereo, but the layout for the left and right eyes is application dependent
+   and must be determined from other data (like the ProjectionPrivate element).
+   */
+  kStereoCustom = 15,
 };
 
 /**