build_api: Implement ImageService/Test

BUG=chromium:905034
TEST=manual, new tests, run_tests

Change-Id: I8e11ca89e63a7a77d66a2f0dfb8ec420aab1091f
Reviewed-on: https://chromium-review.googlesource.com/1432013
Commit-Ready: Alex Klein <saklein@chromium.org>
Tested-by: Alex Klein <saklein@chromium.org>
Reviewed-by: Lann Martin <lannm@chromium.org>
diff --git a/api/build_api.py b/api/build_api.py
index 40da132..fd15ceb 100644
--- a/api/build_api.py
+++ b/api/build_api.py
@@ -17,6 +17,7 @@
 from chromite.api import service
 from chromite.api.gen import build_api_pb2
 from chromite.api.gen import autotest_pb2
+from chromite.api.gen import image_pb2
 from chromite.lib import commandline
 from chromite.lib import cros_build_lib
 from chromite.lib import osutils
@@ -235,6 +236,7 @@
     router (Router): The router.
   """
   router.Register(autotest_pb2)
+  router.Register(image_pb2)
 
 
 def main(argv):