Chromecast buildfix: restores AddKeySystemWithCodecs, fixes namespace.

chromecast/renderer/key_systems_cast.h

Index: chromecast/renderer/key_systems_cast.h
diff --git a/chromecast/renderer/key_systems_cast.h b/chromecast/renderer/key_systems_cast.h
index bd3eec42283a34e20d51629aad1f31337015c81f..f6baa36e2b68adc866988a0fb567ecb099c110fc 100644
--- a/chromecast/renderer/key_systems_cast.h
+++ b/chromecast/renderer/key_systems_cast.h
@@ -12,6 +12,11 @@
 namespace chromecast {
 namespace shell {
 
+// Adds a single key system by name.
+void AddKeySystemWithCodecs(
+    const std::string& key_system_name,
+    std::vector<::media::KeySystemInfo>* concrete_key_systems);
+
 void AddChromecastKeySystems(
     std::vector<::media::KeySystemInfo>* key_systems_info);