Add License::Policy::soft_enforce_playback_duration

[ Merge of http://go/wvgerrit/22564 ]

b/34211676

Test: All unittests other than some oemcrypto, request_license_test
passed. Those tests failed with or without this CL.

Change-Id: I20474339aa1777da2db3677c10f186726505ecc8

libwvdrmengine/cdm/core/src/license_protocol.proto

@@ -82,6 +82,10 @@ message License {
     // Indicates to client that license renewal and release requests ought to
     // include ClientIdentification (client_id).
     optional bool renew_with_client_id = 12 [default = false];
+
+    // Enables "soft enforcement" of playback_duration_seconds, letting the user
+    // finish playback even if short window expires. Optional.
+    optional bool soft_enforce_playback_duration = 14 [default = false];
   }
 
   message KeyContainer {