Setup coverage tool in script with no argument.

R=mmoroz@chromium.org

Change-Id: Ia83a10d1e5c5cb2d81c4bcea2b6839b0e47e1012
Reviewed-on: https://chromium-review.googlesource.com/1042808Reviewed-by: Max Moroz <mmoroz@chromium.org>
Commit-Queue: Max Moroz <mmoroz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#555830}

tools/code_coverage/coverage.py

@@ -1281,6 +1281,11 @@ def Main():
   assert os.path.abspath(os.getcwd()) == SRC_ROOT_PATH, ('This script must be '
                                                          'called from the root '
                                                          'of checkout.')
+
+  # This helps to setup coverage binaries even when script is called with
+  # empty params. This is used by coverage bot for initial setup.
+  DownloadCoverageToolsIfNeeded()
+
   args = _ParseCommandArguments()
   global BUILD_DIR
   BUILD_DIR = args.build_dir
@@ -1304,8 +1309,6 @@ def Main():
   _ValidateBuildingWithClangCoverage()
   _VerifyTargetExecutablesAreInBuildDirectory(args.command)
 
-  DownloadCoverageToolsIfNeeded()
-
   absolute_filter_paths = []
   if args.filters:
     absolute_filter_paths = _VerifyPathsAndReturnAbsolutes(args.filters)