webcrypto: Add ECDSA algorithm (chromium-side)

content/child/webcrypto/jwk.cc

Index: content/child/webcrypto/jwk.cc
diff --git a/content/child/webcrypto/jwk.cc b/content/child/webcrypto/jwk.cc
index d6729caa9b53cf53aab654a8ed0f2ed7e3cc0615..75282f75f0999b760c24eceb98d25fc59da2dfd1 100644
--- a/content/child/webcrypto/jwk.cc
+++ b/content/child/webcrypto/jwk.cc
@@ -448,7 +448,8 @@ JwkWriter::JwkWriter(const std::string& algorithm,
                      bool extractable,
                      blink::WebCryptoKeyUsageMask usages,
                      const std::string& kty) {
-  dict_.SetString("alg", algorithm);
+  if (!algorithm.empty())
+    dict_.SetString("alg", algorithm);
   dict_.Set("key_ops", CreateJwkKeyOpsFromWebCryptoUsages(usages));
   dict_.SetBoolean("ext", extractable);
   dict_.SetString("kty", kty);