Expose a constructor for WebCryptoAlgorithm.

public/platform/WebCryptoAlgorithm.h

Index: public/platform/WebCryptoAlgorithm.h
diff --git a/public/platform/WebCryptoAlgorithm.h b/public/platform/WebCryptoAlgorithm.h
index b1227328af7bebfd1fae24dc06fc25ec2c357b0b..07bcc62c0d1e65a10c59f5c8cb6b7a40b9b8d532 100644
--- a/public/platform/WebCryptoAlgorithm.h
+++ b/public/platform/WebCryptoAlgorithm.h
@@ -75,9 +75,11 @@ class WebCryptoAlgorithm {
 public:
 #if WEBKIT_IMPLEMENTATION
     WebCryptoAlgorithm() { }
-    WebCryptoAlgorithm(WebCryptoAlgorithmId, const char*, PassOwnPtr<WebCryptoAlgorithmParams>);
+    WebCryptoAlgorithm(WebCryptoAlgorithmId, const char* name, PassOwnPtr<WebCryptoAlgorithmParams>);
 #endif
 
+    WEBKIT_EXPORT static WebCryptoAlgorithm adoptParamsAndCreate(WebCryptoAlgorithmId, const char* name, WebCryptoAlgorithmParams*);
+
     ~WebCryptoAlgorithm() { reset(); }
 
     WebCryptoAlgorithm(const WebCryptoAlgorithm& other) { assign(other); }