WebCrypto: Add WebKit API structure for keys.

Source/modules/crypto/Key.idl

Index: Source/modules/crypto/Key.idl
diff --git a/Source/modules/crypto/CryptoOperation.idl b/Source/modules/crypto/Key.idl
similarity index 83%
copy from Source/modules/crypto/CryptoOperation.idl
copy to Source/modules/crypto/Key.idl
index ba683a1b77ed663ff338999db41b9e1e439a4682..f66338594f971250d4e672e49bcf4987b8eb258b 100644
--- a/Source/modules/crypto/CryptoOperation.idl
+++ b/Source/modules/crypto/Key.idl
@@ -28,8 +28,27 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
+enum KeyType {
+    "secret",
+    "public",
+    "private"
+};
+
+enum KeyUsage {
+    "encrypt",
+    "decrypt",
+    "sign",
+    "verify",
+    "derive",
+    "wrap",
+    "unwrap"
+};
+
 [
     NoInterfaceObject,
-] interface CryptoOperation {
+] interface Key {
+    readonly attribute KeyType type;
+    readonly attribute boolean extractable;
     readonly attribute Algorithm algorithm;
+    readonly attribute KeyUsage[] keyUsage;
 };