Get rid of Providers class

inject_common isn't going to be open-sourced anytime soon, so replace it with a
lambda, which wasn't an option when this was originally written we were still
on Java 7 back then.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=213318557

javatests/google/registry/request/RequestHandlerTest.java

@@ -34,7 +34,6 @@ import google.registry.request.auth.AuthResult;
 import google.registry.request.auth.RequestAuthenticator;
 import google.registry.request.auth.UserAuthInfo;
 import google.registry.testing.AppEngineRule;
-import google.registry.testing.Providers;
 import google.registry.testing.UserInfo;
 import java.io.PrintWriter;
 import java.io.StringWriter;
@@ -211,16 +210,18 @@ public final class RequestHandlerTest {
   @Before
   public void before() throws Exception {
     // Initialize here, not inline, so that we pick up the mocked UserService.
-    handler = RequestHandler.createForTest(
-        Component.class,
-        Providers.<Builder>of(new Builder() {
-          @Override
-          public Component build() {
-            // Use a fake Builder that returns the single component instance that uses the mocks.
-            return component;
-          }
-        }),
-        requestAuthenticator);
+    handler =
+        RequestHandler.createForTest(
+            Component.class,
+            () ->
+                new Builder() {
+                  @Override
+                  public Component build() {
+                    // Use a fake Builder that returns the single component instance using the mocks
+                    return component;
+                  }
+                },
+            requestAuthenticator);
     when(rsp.getWriter()).thenReturn(new PrintWriter(httpOutput));
   }
 

javatests/google/registry/testing/Providers.java

@@ -1,29 +0,0 @@
-// 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.testing;
-
-import javax.inject.Provider;
-
-/** Helper functions for {@link Provider}. */
-public final class Providers {
-
-  /**
-   * Returns a {@link Provider} that supplies a constant value.
-   *
-   */
-  public static <T> Provider<T> of(final T instance) {
-    return () -> instance;
-  }
-}