Add ProxyDecryptor which wraps concrete Decryptor implementations.

webkit/media/crypto/key_systems.cc

Index: webkit/media/crypto/key_systems.cc
diff --git a/webkit/media/key_systems.cc b/webkit/media/crypto/key_systems.cc
similarity index 84%
rename from webkit/media/key_systems.cc
rename to webkit/media/crypto/key_systems.cc
index 7efbb9ef9ff073340b4b6f028d2dd8f521507875..b4aeb90b56ce84bb11f981889a09abd04ea78a84 100644
--- a/webkit/media/key_systems.cc
+++ b/webkit/media/crypto/key_systems.cc
@@ -2,8 +2,10 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "webkit/media/key_systems.h"
+#include "webkit/media/crypto/key_systems.h"
 
+#include "media/base/decryptor.h"
+#include "media/crypto/aes_decryptor.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/platform/WebString.h"
 
 namespace webkit_media {
@@ -75,4 +77,11 @@ bool IsSupportedKeySystemWithMediaMimeType(
   return true;
 }
 
+scoped_ptr<media::Decryptor> CreateDecryptor(const std::string& key_system,
+                                             media::DecryptorClient* client) {
+  if (key_system == kClearKeyKeySystem)
+    return scoped_ptr<media::Decryptor>(new media::AesDecryptor(client));
+  return scoped_ptr<media::Decryptor>();
+}
+
 }  // namespace webkit_media