[webcrypto] Add JWK RSA public key export for NSS.

content/child/webcrypto/platform_crypto_openssl.cc

Index: content/child/webcrypto/platform_crypto_openssl.cc
diff --git a/content/child/webcrypto/platform_crypto_openssl.cc b/content/child/webcrypto/platform_crypto_openssl.cc
index 5fdee3965c814dd3959ab692829af26292d48b0c..a3f139cc4910070167cf18c938358e2371840192 100644
--- a/content/child/webcrypto/platform_crypto_openssl.cc
+++ b/content/child/webcrypto/platform_crypto_openssl.cc
@@ -387,6 +387,15 @@ Status ExportKeySpki(PublicKey* key, blink::WebArrayBuffer* buffer) {
   return Status::ErrorUnsupported();
 }
 
+// Preconditions:
+//  * |key| is non-null.
+Status ExportRsaPublicKey(PublicKey* key,
+                          std::vector<uint8>* modulus,
+                          std::vector<uint8>* public_exponent) {
+  // TODO(eroman): http://crbug.com/267888
+  return Status::ErrorUnsupported();
+}
+
 Status WrapSymKeyAesKw(SymKey* wrapping_key,
                        SymKey* key,
                        blink::WebArrayBuffer* buffer) {