[webcrypto] Implement AES-CTR using BoringSSL.

content/child/webcrypto/nss/util_nss.cc

Index: content/child/webcrypto/nss/util_nss.cc
diff --git a/content/child/webcrypto/nss/util_nss.cc b/content/child/webcrypto/nss/util_nss.cc
index dd0ef3c3d35a1e93a10f672f7886056751c21c3c..eb516e049a0b61804939db1b940f5a90ebf7fbe9 100644
--- a/content/child/webcrypto/nss/util_nss.cc
+++ b/content/child/webcrypto/nss/util_nss.cc
@@ -6,6 +6,7 @@
 
 #include "base/lazy_instance.h"
 #include "content/child/webcrypto/crypto_data.h"
+#include "content/child/webcrypto/platform_crypto.h"
 #include "crypto/nss_util.h"
 #include "crypto/scoped_nss_types.h"
 
@@ -79,6 +80,11 @@ void PlatformInit() {
   crypto::EnsureNSSInit();
 }
 
+AlgorithmImplementation* CreatePlatformAesCtrImplementation() {
+  // TODO(eroman): http://crbug.com/399084
+  return NULL;
+}
+
 }  // namespace webcrypto
 
 }  // namespace content