Cherry pick 18.4 changes to udc-widevine-dev

Get the udc-widevine-dev Android branch and oemcrypto-v18 cdm branch in
sync. The commit ID for 18.4 on oemcrypto-v18 is
a2f23a2281e5e06dc2867585bdc516fa132b6396.

Merged from go/wvgerrit/190151

Bug: 290252845
Test: WVTS tests are running and passing
Change-Id: I457332e7ca70a5b5169345e1279b3eb9f18413b6

libwvdrmengine/oemcrypto/util/test/oemcrypto_ref_test_utils.cpp

@@ -0,0 +1,20 @@
+// 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 utilities of OEMCrypto APIs
+//
+#include "oemcrypto_ref_test_utils.h"
+
+#include <string>
+
+#include "cdm_random.h"
+
+namespace wvoec {
+namespace util {
+std::vector<uint8_t> RandomData(size_t length) {
+  const std::string data = wvutil::CdmRandom::RandomData(length);
+  return std::vector<uint8_t>(data.begin(), data.end());
+}
+}  // namespace util
+}  // namespace wvoec