Add a marker interface for NodeEntries wrapped by NotifyingHelper.

Add a marker interface to identify NodeEntries created by tests. Mark NodeEntry
wrappers created by NotifyingHelper with the new interface.

PiperOrigin-RevId: 305147884

src/main/java/com/google/devtools/build/skyframe/TestOnlyNodeEntry.java

@@ -0,0 +1,21 @@
+// Copyright 2020 The Bazel 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 com.google.devtools.build.skyframe;
+
+/** {@link NodeEntry} wrapper created by test helpers. */
+public interface TestOnlyNodeEntry extends NodeEntry {
+  /** Retrieves the original {@link NodeEntry} wrapped by the test node. */
+  NodeEntry getDelegate();
+}

src/test/java/com/google/devtools/build/skyframe/NotifyingHelper.java

@@ -219,7 +219,7 @@ public void accept(SkyKey key, EventType type, Order order, @Nullable Object con
   }
 
   /** {@link NodeEntry} that informs a {@link Listener} of various method calls. */
-  protected class NotifyingNodeEntry extends DelegatingNodeEntry {
+  protected class NotifyingNodeEntry extends DelegatingNodeEntry implements TestOnlyNodeEntry {
     private final SkyKey myKey;
     private final ThinNodeEntry delegate;
 
@@ -229,7 +229,7 @@ protected NotifyingNodeEntry(SkyKey key, ThinNodeEntry delegate) {
     }
 
     @Override
-    protected NodeEntry getDelegate() {
+    public NodeEntry getDelegate() {
       return (NodeEntry) delegate;
     }