Emphasize that default_strict_deps_java_protos is subject to change at any time without prior notice.

--
MOS_MIGRATED_REVID=129409727

src/main/java/com/google/devtools/build/lib/packages/PackageFactory.java

diff --git a/src/main/java/com/google/devtools/build/lib/packages/PackageFactory.java b/src/main/java/com/google/devtools/build/lib/packages/PackageFactory.java
index 995e92e..4c3138a 100644
--- a/src/main/java/com/google/devtools/build/lib/packages/PackageFactory.java
+++ b/src/main/java/com/google/devtools/build/lib/packages/PackageFactory.java
@@ -265,6 +265,9 @@
   /**
    * Declares the package() attribute specifying the default value for
    * java_proto_library.strict_deps.
+   *
+   * <p>This attribute should be considered as undocumented/experimental, and is subject to change
+   * at any time without prior notice.
    */
   private static class DefaultStrictDepsJavaProtos extends PackageArgument<Boolean> {
     private DefaultStrictDepsJavaProtos() {