Add API for device provisioning server certificate

[ Merge of http://go/wvgerrit/20205/ ]

This is separate from the server certificate used for license
requests.

b/34211823

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

Change-Id: I23abdf276f8d3db9222f014175d0bb5094010a04

libwvdrmengine/mediadrm/include/WVDrmPlugin.h

@@ -215,6 +215,16 @@ class WVDrmPlugin : public android::DrmPlugin,
       mServiceCertificate = serviceCertificate;
     }
 
+    virtual const std::string& device_provisioning_service_certificate() const {
+      // Android does not support service certificates for provisioning.
+      return mEmptyString;
+    }
+
+    virtual void set_device_provisioning_service_certificate(
+        const std::string& ) {
+      // Ignore. Android does not support service certificates for provisioning
+    }
+
     virtual bool is_session_sharing_enabled() const {
       return mShareKeys;
     }
@@ -248,6 +258,7 @@ class WVDrmPlugin : public android::DrmPlugin,
     bool mShareKeys;
     uint32_t mSessionSharingId;
     std::string mAppId;
+    const std::string mEmptyString;
   } mPropertySet;
 
   android::sp<wvcdm::WvContentDecryptionModule> const mCDM;