compare_build_artifacts.py should compare .isolated files

The option --use-isolate-files causes compare_build_artifacts.py to
compare the files referenced by .isolate. It should also compare the
contents of .isolated files.

Bug: 876915
Change-Id: I06eb0d3373493db90b75befe9e0b47c9de58cbe0
Reviewed-on: https://chromium-review.googlesource.com/1185991Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: Erik Chen <erikchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#585330}

tools/determinism/compare_build_artifacts.py

@@ -81,6 +81,10 @@ def get_files_to_compare_using_isolate(build_dir):
           for inner_file in files:
             ret_files.add(os.path.join(root, inner_file))
 
+  # Also add any .isolated files that exist.
+  for isolated in glob.glob(os.path.join(build_dir, '*.isolated')):
+    ret_files.add(isolated)
+
   # Convert back to a relpath since that's what the caller is expecting.
   return set(os.path.relpath(f, build_dir) for f in ret_files)