Add support for legacy ECDSA private keys to certificate_view.h

NOKEYCHECK

PiperOrigin-RevId: 323862773
Change-Id: If8a9265debe9f3fd2b2c22ea4eaffb01a05c787e
diff --git a/quic/test_tools/test_certificates.h b/quic/test_tools/test_certificates.h
index e7d3035..f617941 100644
--- a/quic/test_tools/test_certificates.h
+++ b/quic/test_tools/test_certificates.h
@@ -43,6 +43,9 @@
 QUIC_CONST_INIT extern const quiche::QuicheStringPiece
     kWildcardCertificatePrivateKey;
 
+// PEM-encoded P-256 private key using legacy OpenSSL encoding.
+QUIC_CONST_INIT extern const char kTestEcPrivateKeyLegacyPem[];
+
 }  // namespace test
 }  // namespace quic