dependency: List endpoint return reverse dependencies.

Have the List endpoint return reverse dependencies by default. Currently
the only use case of the endpoint is slim builds.

BUG=chromium:1149921, b:178484769
TEST=./run_pytest

Change-Id: I3f6a736a7b729493474a302ac729000cbd8d4339
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/2775290
Tested-by: Navil Perez <navil@google.com>
Reviewed-by: Michael Mortensen <mmortensen@google.com>
Commit-Queue: Navil Perez <navil@google.com>
diff --git a/api/controller/dependency.py b/api/controller/dependency.py
index dc72374..ae0aaf1 100644
--- a/api/controller/dependency.py
+++ b/api/controller/dependency.py
@@ -119,7 +119,8 @@
       packages=[
           controller_util.deserialize_package_info(package)
           for package in input_proto.packages
-      ])
+      ],
+      include_rev_dependencies=True)
   for package in package_deps:
     pkg_info_msg = output_proto.package_deps.add()
     controller_util.serialize_package_info(package, pkg_info_msg)