Added unittests for reference ECC implementation.

[ Merge of http://go/wvgerrit/114284 ]

The unittests check that the ECC keys are being created as expected
and that they can perform their basic operations.

Bug: 135283522
Test: oemcrypto_unittests
Change-Id: I1bdb26421ba47e1ab135f5ce5a54da304627a7c3

libwvdrmengine/oemcrypto/ref/test/oemcrypto_ref_test_utils.h

@@ -0,0 +1,21 @@
+// Copyright 2021 Google LLC. All Rights Reserved. This file and proprietary
+// source code may only be used and distributed under the Widevine License
+// Agreement.
+//
+//  Reference implementation of OEMCrypto APIs
+//
+#ifndef OEMCRYPTO_REF_TEST_UTILS_H_
+#define OEMCRYPTO_REF_TEST_UTILS_H_
+
+#include <stdint.h>
+
+#include <vector>
+
+namespace wvoec_ref {
+
+// Returns a vector of random bytes.
+std::vector<uint8_t> RandomData(size_t length);
+
+}  // namespace wvoec_ref
+
+#endif  // OEMCRYPTO_REF_TEST_UTILS_H_