[media] Make HDR10+ side data type explicit (#3224)

kMatroskaBlockAdditional is the only side data type supported by Cobalt
and its value happens to be 0. The setup of the SbPlayerSampleSideData
inside SbPlayerBridge didn't explicitly set the side data type, and
relies on the value of kMatroskaBlockAdditional is 0 as it
zero-initialized the struct.

Now the type is explicitly set.

b/276483058

Change-Id: I1d532d2537df02b3fc2af31dda8abb590c396d8e

cobalt/media/base/sbplayer_bridge.cc

@@ -946,6 +946,7 @@ void SbPlayerBridge::WriteBuffersInternal(
 
     if (buffer->side_data_size() > 0) {
       // We only support at most one side data currently.
+      side_data->type = kMatroskaBlockAdditional;
       side_data->data = buffer->side_data();
       side_data->size = buffer->side_data_size();
       sample_info.side_data = side_data;