binder: Support DER format certificates.

Test: binderRpcTest
Bug: 195166979

Change-Id: I78b4d2b1207819a9cf9eadf099e2c44cfaac8096
diff --git a/libs/binder/tests/binderRpcTest.cpp b/libs/binder/tests/binderRpcTest.cpp
index 8c805bb..8ffd68d 100644
--- a/libs/binder/tests/binderRpcTest.cpp
+++ b/libs/binder/tests/binderRpcTest.cpp
@@ -1730,6 +1730,7 @@
 std::vector<CertificateFormat> testCertificateFormats() {
     return {
             CertificateFormat::PEM,
+            CertificateFormat::DER,
     };
 }