code-coverage: Gather code coverage artifacts

Update the ArtifactService.Get method to bundle CODE_COVERAGE_LLVM_JSON
artifacts so that they can be used by recipes.

BUG=b:187794906
TEST=./run_tests && ./api/contrib/artifacts__get

Change-Id: I95d1459ca546052250d1a6de854c08bc42d40d37
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/2992106
Tested-by: David Welling <davidwelling@google.com>
Auto-Submit: David Welling <davidwelling@google.com>
Commit-Queue: David Welling <davidwelling@google.com>
Reviewed-by: LaMont Jones <lamontjones@chromium.org>
Reviewed-by: Alex Klein <saklein@chromium.org>
diff --git a/api/controller/artifacts.py b/api/controller/artifacts.py
index 6c51d4f..f46bb4f 100644
--- a/api/controller/artifacts.py
+++ b/api/controller/artifacts.py
@@ -13,6 +13,7 @@
 from chromite.api.controller import controller_util
 from chromite.api.controller import image as image_controller
 from chromite.api.controller import sysroot as sysroot_controller
+from chromite.api.controller import test as test_controller
 from chromite.api.gen.chromite.api import artifacts_pb2
 from chromite.api.gen.chromite.api import toolchain_pb2
 from chromite.api.gen.chromiumos import common_pb2
@@ -80,7 +81,11 @@
           output_proto.artifacts.sysroot,
           sysroot_controller.GetArtifacts(
               input_proto.artifact_info.sysroot, chroot, sysroot, build_target,
-              output_dir))
+              output_dir)),
+      RegisteredGet(
+          output_proto.artifacts.test,
+          test_controller.GetArtifacts(
+              input_proto.artifact_info.test, chroot, sysroot, output_dir)),
   ]
 
   for get_res in get_res_list: