Have determine_chrome_version use a build_target to match controller call.

BUG=chromium:1015064
TEST=manual, run_tests

Change-Id: Ic6c98ff129441ffe2bf6c289633041bfa9e6ee05
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/1865528
Reviewed-by: Alex Klein <saklein@chromium.org>
Tested-by: Michael Mortensen <mmortensen@google.com>
Commit-Queue: Michael Mortensen <mmortensen@google.com>
diff --git a/service/packages.py b/service/packages.py
index 9a904cf..7852d18 100644
--- a/service/packages.py
+++ b/service/packages.py
@@ -435,13 +435,13 @@
   return any(atom in package for package in graph['package_deps'])
 
 
-def determine_chrome_version(board):
+def determine_chrome_version(build_target):
   """Returns the current Chrome version for the board (or in buildroot).
 
   Args:
-    board: The board name this is specific to.
+    build_target (build_target_util.BuildTarget): The board build target.
   """
-  cpv = portage_util.PortageqBestVisible(constants.CHROME_CP, board,
+  cpv = portage_util.PortageqBestVisible(constants.CHROME_CP, build_target.name,
                                          cwd=constants.SOURCE_ROOT)
   # Something like 78.0.3877.4_rc -> 78.0.3877.4
   return cpv.version_no_rev.partition('_')[0]