Add vendor_partitions artifact support for devserver

vendor_partitions artifact is needed for Brillo provision.

BUG=None
TEST=loca run devserver
curl http://127.0.0.1:8082/stage?target=dragonboard-userdebug\&build_id=2453994\&artifacts=vendor_partitions\&branch=git_mnc-brillo-dev\&os_type=android

Change-Id: Ie1176ff77137d4623d3d6e498b29667d181d289e
Reviewed-on: https://chromium-review.googlesource.com/315194
Commit-Ready: Dan Shi <dshi@google.com>
Tested-by: Dan Shi <dshi@chromium.org>
Reviewed-by: Chris Sosa <sosa@chromium.org>
diff --git a/artifact_info.py b/artifact_info.py
index 3e63c49..35fdba0 100644
--- a/artifact_info.py
+++ b/artifact_info.py
@@ -91,6 +91,9 @@
 # Test zip file for Android build, e.g., shamu-tests-2284311.zip
 ANDROID_TEST_ZIP = 'test_zip'
 
+# Zip file of vendor partitions used by Brillo device.
+ANDROID_VENDOR_PARTITION_ZIP = 'vendor_partitions'
+
 # In general, downloading one artifact usually indicates that the caller will
 # want to download other artifacts later. The following map explicitly defines
 # this relationship. Specifically: