Support CAST V2 authentication

bug: 12702350

Squashed commit of these CLs from the widevine cdm repo:

Cast V2 cdm support
https://widevine-internal-review.googlesource.com/#/c/9190/

Add CASTv2 Support to DrmPlugin
https://widevine-internal-review.googlesource.com/#/c/9228/

Test for CastV2 authentication APIs
https://widevine-internal-review.googlesource.com/9550

Change-Id: I6d66bc1bbd653db5542c68687b30b441dd20617f

libwvdrmengine/cdm/core/src/license_protocol.proto

@@ -292,15 +292,38 @@ message SessionState {
 //   Public protocol buffer definitions for Widevine Device Certificate
 //   Provisioning protocol.
 
+// PROPOSED message for customizing provisioning request.
+// This could support requesting specificy types of certificates.
+// E.g. Cast X.509 certs.
+message ProvisioningOptions {
+  // PROPOSED enum identifying the certificate type.
+  enum CertificateType {
+    RSA_WIDEVINE = 0; // Default.  The original certificate type.
+    X509 = 1; // X.509 certificate.
+  }
+
+  optional CertificateType certificate_type = 1;
+
+  // OPEN QUESTION: How does the client specify the cert root authority?
+  // Should this be the cert authority's domain?  E.g. foo.com?
+  optional string certificate_authority = 2;
+}
+
 // Provisioning request sent by client devices to provisioning service.
 message ProvisioningRequest {
   // Device root of trust and other client identification. Required.
   optional ClientIdentification client_id = 1;
   // Nonce value used to prevent replay attacks. Required.
   optional bytes nonce = 2;
+  // Options for type of certificate to generate.  Optional.
+  optional ProvisioningOptions options = 3;
 }
 
 // Provisioning response sent by the provisioning server to client devices.
+//
+// PROPOSAL: The contents of this message vary depending upon the value of
+// CertificateType in options.  TODO(blueeyes): Determine the right way to
+// transfer X.509 certs.
 message ProvisioningResponse {
   // AES-128 encrypted device private RSA key. PKCS#1 ASN.1 DER-encoded.
   // Required.