Fix ECDSA upcalls from TLS/SSL into JCA.

When BoringSSL/OpenSSL TLS/SSL stack operates on opaque private keys
(those that don't expose their key material) it upcalls (via
Conscrypt's NativeCrypto) into corresponding JCA Signature and Cipher
primitives.

This fixes a crash in the ECDSA upcall when Conscrypt is used with
BoringSSL.

(cherry-picked from commit 61c66eb9842dd689dea2701124147c4197c95c90)

Bug: 21738458
Change-Id: I6def1bce62f20b2ec39fe88251975458e8813362
1 file changed