Always generate nonce before signing license

Merge from Widevine repo of http://go/wvgerrit/135467

The v16 state diagram says that a nonce should be included in all
license requests. The unit tests were not honoring this
requirement. This CL updates the unit tests to match the
spec.

Test: ran unit tests on luci
Bug: 186565384
Change-Id: Ib3e03593538235e2eae3da1732109f0e9bfd97bd

libwvdrmengine/oemcrypto/test/oec_session_util.h

@@ -218,6 +218,9 @@ class RoundTrip {
   }
 
  protected:
+  // Returns true if a nonce should be generated before signing the request.
+  virtual bool RequestHasNonce() = 0;
+
   // ----------------------------------------------------------------------
   // Specialized functionality for each message type.
 
@@ -281,6 +284,7 @@ class ProvisioningRoundTrip
   void InjectFuzzedResponseData(const uint8_t* data, size_t size);
 
  protected:
+  bool RequestHasNonce() override { return true; }
   void VerifyRequestSignature(const vector<uint8_t>& data,
                               const vector<uint8_t>& generated_signature,
                               size_t core_message_length) override;
@@ -388,6 +392,7 @@ class LicenseRoundTrip
   void SetKeyId(size_t index, const string& key_id);
 
  protected:
+  bool RequestHasNonce() override { return true; }
   void VerifyRequestSignature(const vector<uint8_t>& data,
                               const vector<uint8_t>& generated_signature,
                               size_t core_message_length) override;
@@ -451,6 +456,7 @@ class RenewalRoundTrip
   void set_is_release(bool is_release) { is_release_ = is_release; }
 
  protected:
+  bool RequestHasNonce() override { return false; }
   void VerifyRequestSignature(const vector<uint8_t>& data,
                               const vector<uint8_t>& generated_signature,
                               size_t core_message_length) override;
@@ -508,6 +514,8 @@ class Session {
   // Returns the most recently generated nonce.
   // Valid after call to GenerateNonce.
   uint32_t nonce() const { return nonce_; }
+  // The nonce can be overridden.
+  void set_nonce(uint32_t nonce) { nonce_ = nonce; }
   // Valid after call to open().
   uint32_t session_id() const { return (uint32_t)session_id_; }
   // Call OEMCrypto_OpenSession, with GTest ASSERTs.