Corrections to support HLS

[ Merge of https://go/wvgerrit/17055 ]

There are a few bugs that need to be addressed to get HLS to work.

* Content ID in json init data is base64 encoded and needs to be decoded
  before being added to the WidevineCencHeader proto.
* Protection scheme was not set in the WidevineCencHeader proto.
* HLS initialization data should be sent as a CENC content identification
  in a license request.

b/20630275

Change-Id: Ie0ac33ac061931df6f26c0afbf3e62e5d01e5041

libwvdrmengine/cdm/core/src/license.cpp

@@ -246,7 +246,7 @@ CdmResponseType CdmLicense::PrepareKeyRequest(
   LicenseRequest_ContentIdentification* content_id =
       license_request.mutable_content_id();
 
-  if (init_data.is_cenc()) {
+  if (init_data.is_cenc() || init_data.is_hls()) {
     LicenseRequest_ContentIdentification_CENC* cenc_content_id =
         content_id->mutable_cenc_id();