Support for the new WebCrypto digest by chunks API.

content/child/webcrypto/shared_crypto.cc

Index: content/child/webcrypto/shared_crypto.cc
diff --git a/content/child/webcrypto/shared_crypto.cc b/content/child/webcrypto/shared_crypto.cc
index 92aa342b321eb3f78adeed61e5a47dff2e5bda21..0b211492159b4d8e86892fd04386b8013e7cdb61 100644
--- a/content/child/webcrypto/shared_crypto.cc
+++ b/content/child/webcrypto/shared_crypto.cc
@@ -535,6 +535,11 @@ Status Digest(const blink::WebCryptoAlgorithm& algorithm,
   }
 }
 
+scoped_ptr<blink::WebCryptoDigestor> CreateDigestor(
+    blink::WebCryptoAlgorithmId algorithm) {
+  return platform::CreateDigestor(algorithm);
+}
+
 Status GenerateSecretKey(const blink::WebCryptoAlgorithm& algorithm,
                          bool extractable,
                          blink::WebCryptoKeyUsageMask usage_mask,