Make InMemoryGraph public.

PiperOrigin-RevId: 162788157
diff --git a/src/main/java/com/google/devtools/build/skyframe/InMemoryGraph.java b/src/main/java/com/google/devtools/build/skyframe/InMemoryGraph.java
index 7b0f56c..e8c7d35 100644
--- a/src/main/java/com/google/devtools/build/skyframe/InMemoryGraph.java
+++ b/src/main/java/com/google/devtools/build/skyframe/InMemoryGraph.java
@@ -17,7 +17,7 @@
 import javax.annotation.Nullable;
 
 /** {@link ProcessableGraph} that exposes the contents of the entire graph. */
-interface InMemoryGraph extends ProcessableGraph {
+public interface InMemoryGraph extends ProcessableGraph {
   @Override
   Map<SkyKey, ? extends NodeEntry> createIfAbsentBatch(
       @Nullable SkyKey requestor, Reason reason, Iterable<SkyKey> keys);