Replace KeystoreKeyring with KmsKeystore comparison

Replace KeystoreKeyring with ComparatorKeyring between KeystoreKeyring and
KmsKeystore. In the opensource version, will replace DummyKeyring with
KmsKeyring directly.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=152893767

java/google/registry/keyring/kms/KeyringModule.java

@@ -0,0 +1,34 @@
+// Copyright 2017 The Nomulus Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package google.registry.keyring.kms;
+
+import dagger.Module;
+import dagger.Provides;
+
+import google.registry.keyring.api.Keyring;
+
+import javax.inject.Singleton;
+
+/** Dagger module for {@link Keyring} */
+@Module
+public final class KeyringModule {
+
+  @Provides
+  @Singleton
+  // TODO(b/35810650): return kmsKeyring directly once comparison period is over.
+  public static Keyring provideKeyring(KmsKeyring kmsKeyring) {
+    return kmsKeyring;
+  }
+}