check-webkit-style doesn't fail when all files are skipped.

Currently 'git cl uplaod' fails when all files are skipped (e.g. fixing
LayoutTest). This patch makes it pass.

Bug: none
Change-Id: Ib028d39ed63e0cba21918cb565a5c264ad047da7
Reviewed-on: https://chromium-review.googlesource.com/923782Reviewed-by: Kent Tamura <tkent@chromium.org>
Commit-Queue: Makoto Shimazu <shimazu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#537270}

third_party/WebKit/Tools/Scripts/webkitpy/style/main.py

@@ -158,5 +158,5 @@ class CheckWebKitStyle(object):
         delete_only_file_count = file_reader.delete_only_file_count
 
         _log.info('Total errors found: %d in %d files', error_count, file_count)
-        # We fail when style errors are found or there are no checked files.
-        return error_count > 0 or (file_count == 0 and delete_only_file_count == 0)
+        # We fail when style errors are found.
+        return error_count > 0