fix: Fix key rotation in DASH

This was broken accidentally during MediaCapabilities refactoring.
This does not affect any release version.

The filtering step does two things: it applys the "restrictions"
config to the streams in the manifest, and it sends DRM init data to
DrmEngine for all streams in case new sessions need to be created.

For key rotation, it is critical to create new sessions in DrmEngine.
The init datas for new periods are added to existing streams when the
new period's streams are stitched onto the old ones.

The restrictions config should also be applied on manifest update,
since the update could have created some new streams with
characteristics outside of the current restrictions config.

Closes shaka-project#3169

Change-Id: I716c2978c7394d7bb56227aa1854392a10eae058

lib/dash/dash_parser.js

@@ -485,6 +485,11 @@ shaka.dash.DashParser = class {
       this.manifest_.variants = this.periodCombiner_.getVariants();
       this.manifest_.textStreams = this.periodCombiner_.getTextStreams();
       this.manifest_.imageStreams = this.periodCombiner_.getImageStreams();
+
+      // Re-filter the manifest.  This will check any configured restrictions on
+      // new variants, and will pass any new init data to DrmEngine to ensure
+      // that key rotation works correctly.
+      this.playerInterface_.filter(this.manifest_);
     }
 
     // Add text streams to correspond to closed captions.  This happens right