Document FileResource

Change-Id: I2048bbda1b9585a32de8c80fef6608cd94c2b38d
diff --git a/java/com/google/gerrit/server/project/FileResource.java b/java/com/google/gerrit/server/project/FileResource.java
index 6e5375a..e8926dc 100644
--- a/java/com/google/gerrit/server/project/FileResource.java
+++ b/java/com/google/gerrit/server/project/FileResource.java
@@ -27,6 +27,11 @@
 import org.eclipse.jgit.revwalk.RevWalk;
 import org.eclipse.jgit.treewalk.TreeWalk;
 
+/**
+ * A file.
+ *
+ * <p>This is in the project package because it is accessed through the project/branch/file path.
+ */
 public class FileResource implements RestResource {
   public static final TypeLiteral<RestView<FileResource>> FILE_KIND =
       new TypeLiteral<RestView<FileResource>>() {};