Merge Widevine CDM-Side Core Changes

This is a combined merge of several small changes to the core in the
Widevine CDM repository:

http://go/wvgerrit/10941
  Rename privacy_crypto to allow more variants.

http://go/wvgerrit/11530
  Add Missing Header to properties.h

http://go/wvgerrit/11531
  More Loosely Couple CdmEngine and CdmSession

Change-Id: I5b3f738ae495ab267da1440421dd7aa6f7860194

libwvdrmengine/cdm/core/include/cdm_engine.h

@@ -5,7 +5,6 @@
 
 #include <string>
 
-#include "cdm_session.h"
 #include "certificate_provisioning.h"
 #include "crypto_session.h"
 #include "initialization_data.h"
@@ -17,6 +16,7 @@
 namespace wvcdm {
 
 class CdmClientPropertySet;
+class CdmSession;
 class CryptoEngine;
 class UsagePropertySet;
 class WvCdmEventListener;