Mac: implement <keygen> support, including adding generated cert to the Keychain.

net/base/keygen_handler.h

 // Copyright (c) 2009 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef NET_BASE_KEYGEN_HANDLER_H_
 #define NET_BASE_KEYGEN_HANDLER_H_
 
 #include <string>
 
 namespace net {
 
 // This class handles keypair generation for generating client
-// certificates via the Netscape <keygen> tag.
+// certificates via the <keygen> tag.
+// <http://dev.w3.org/html5/spec/Overview.html#the-keygen-element>
+// <https://developer.mozilla.org/En/HTML/HTML_Extensions/KEYGEN_Tag>
 
 class KeygenHandler {
  public:
-  KeygenHandler(int key_size_index, const std::string& challenge);
+  // Creates a handler that will generate a key with the given key size
+  // and incorporate the |challenge| into the Netscape SPKAC structure.
+  inline KeygenHandler(int key_size_in_bits, const std::string& challenge);
+
+  // Actually generates the key-pair and the cert request (SPKAC), and returns
+  // a base64-encoded string suitable for use as the form value of <keygen>.
   std::string GenKeyAndSignChallenge();
 
+  // Exposed only for unit tests.
+  void set_stores_key(bool store) { stores_key_ = store;}
+
  private:
-  int key_size_index_;
-  std::string challenge_;
+  int key_size_in_bits_;  // key size in bits (usually 2048)
+  std::string challenge_;  // challenge string sent by server
+  bool stores_key_;  // should the generated key-pair be stored persistently?
 };
 
+KeygenHandler::KeygenHandler(int key_size_in_bits,
+                             const std::string& challenge)
+    : key_size_in_bits_(key_size_in_bits),
+      challenge_(challenge),
+      stores_key_(true) {
+}
+
 }  // namespace net
 
 #endif  // NET_BASE_KEYGEN_HANDLER_H_