Offline playback for fastball

[ Merge of http://go/wvgerrit/18560 ]

This adds support for offline playback. If the content contains
mutiple playlists which contain differing EXT-X-KEY attribute lists,
each of those keys will need to be saved and restored into separate
sessions.

b/30041089

Test: Added unit tests to cover new functionality. Some oem_crypto,
request_license_test failures but the same as without this CL.

Change-Id: Ia1b877e12a67e8a720d29897ac7e2da236090123

libwvdrmengine/cdm/core/src/device_files.proto

@@ -52,11 +52,21 @@ message UsageInfo {
   repeated ProviderSession sessions = 1;
 }
 
+message HlsAttributes {
+  enum Method  {
+    AES_128 = 1;
+    SAMPLE_AES = 2;
+  }
+  optional Method method = 1;
+  optional bytes media_segment_iv = 2;
+}
+
 message File {
   enum FileType {
     DEVICE_CERTIFICATE = 1;
     LICENSE = 2;
     USAGE_INFO = 3;
+    HLS_ATTRIBUTES = 4;
   }
 
   enum FileVersion {
@@ -68,6 +78,7 @@ message File {
   optional DeviceCertificate device_certificate = 3;
   optional License license = 4;
   optional UsageInfo usage_info = 5;
+  optional HlsAttributes hls_attributes = 6;
 }
 
 message HashedFile {