Increase the visibility of TreeArtifactValue.

PiperOrigin-RevId: 224331734
diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/TreeArtifactValue.java b/src/main/java/com/google/devtools/build/lib/skyframe/TreeArtifactValue.java
index 386845a..9e581f42 100644
--- a/src/main/java/com/google/devtools/build/lib/skyframe/TreeArtifactValue.java
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/TreeArtifactValue.java
@@ -42,7 +42,7 @@
  * {@link TreeFileArtifact}s.
  */
 @AutoCodec
-class TreeArtifactValue implements SkyValue {
+public class TreeArtifactValue implements SkyValue {
   private static final Function<Artifact, PathFragment> PARENT_RELATIVE_PATHS =
       new Function<Artifact, PathFragment>() {
         @Override
@@ -231,12 +231,13 @@
   }
 
   /**
-   * Recursively get all child files in a directory
-   * (excluding child directories themselves, but including all files in them).
-   * @throws IOException if there is any problem reading or validating outputs under the given
-   *     tree artifact.
+   * Recursively get all child files in a directory (excluding child directories themselves, but
+   * including all files in them).
+   *
+   * @throws IOException if there is any problem reading or validating outputs under the given tree
+   *     artifact.
    */
-  static Set<PathFragment> explodeDirectory(Path treeArtifactPath) throws IOException {
+  public static Set<PathFragment> explodeDirectory(Path treeArtifactPath) throws IOException {
     ImmutableSet.Builder<PathFragment> explodedDirectory = ImmutableSet.builder();
     explodeDirectory(treeArtifactPath, PathFragment.EMPTY_FRAGMENT, explodedDirectory);
     return explodedDirectory.build();