WebCrypto: Add interface for exportKey().

Source/modules/crypto/SubtleCrypto.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 158 matching lines @@
     if (!normalizeAlgorithm(rawAlgorithm, ImportKey, algorithm, es))
         return ScriptObject();
 
     const unsigned char* keyDataBytes = static_cast<unsigned char*>(keyData->baseAddress());
 
     RefPtr<CryptoResult> result = CryptoResult::create();
     WebKit::Platform::current()->crypto()->importKey(format, keyDataBytes, keyData->byteLength(), algorithm, extractable, keyUsages, result->result());
     return result->promise();
 }
 
+ScriptObject SubtleCrypto::exportKey(const String& rawFormat, Key* key, ExceptionState& es)
+{
+    WebKit::WebCryptoKeyFormat format;
+    if (!Key::parseFormat(rawFormat, format, es))
+        return ScriptObject();
+
+    if (!key) {
+        es.throwTypeError("Invalid key argument");
+        return ScriptObject();
+    }
+
+    if (!key->extractable()) {
+        es.throwDOMException(NotSupportedError, "key is not extractable");
+        return ScriptObject();
+    }
+
+    RefPtr<CryptoResult> result = CryptoResult::create();
+    WebKit::Platform::current()->crypto()->exportKey(format, key->key(), result->result());
+    return result->promise();
+}
+
 } // namespace WebCore