WebCrypto: Add interface for exportKey().

Source/testing/runner/MockWebCrypto.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 107 matching lines @@
     if (keyDataString == "error")
         return result.completeWithError();
 
     WebKit::WebCryptoKeyType type = WebKit::WebCryptoKeyTypePrivate;
     if (keyDataString == "public")
         type = WebKit::WebCryptoKeyTypePublic;
 
     result.completeWithKey(WebKit::WebCryptoKey::create(0, type, extractable, algorithm, usages));
 }
 
+void MockWebCrypto::exportKey(WebKit::WebCryptoKeyFormat format, const WebKit::WebCryptoKey& key, WebKit::WebCryptoResult result)
+{
+    std::string buffer;
+
+    if (format == WebKit::WebCryptoKeyFormatRaw)
+        buffer = "raw";
+    else if (format == WebKit::WebCryptoKeyFormatPkcs8)
+        buffer = "pkcs8";
+
+    result.completeWithBuffer(buffer.data(), buffer.size());
+}
+
+
 } // namespace WebTestRunner