Add gts-tests as a test sub-path so check_style applies test lint logic to it.

Test: n/a
Change-Id: I1117008888c75b6e59ed8ec74c500ec6523c7fb7
diff --git a/checkstyle.py b/checkstyle.py
index a73c7da..7907001 100755
--- a/checkstyle.py
+++ b/checkstyle.py
@@ -62,7 +62,7 @@
                 'com.puppycrawl.tools.checkstyle.checks.imports.UnusedImportsCheck']
 SKIPPED_RULES_FOR_TEST_FILES = ['com.puppycrawl.tools.checkstyle.checks.javadoc.JavadocTypeCheck',
                                 'com.puppycrawl.tools.checkstyle.checks.javadoc.JavadocMethodCheck']
-SUBPATH_FOR_TEST_FILES = ['/tests/', '/test/', '/androidTest/', '/perftests/']
+SUBPATH_FOR_TEST_FILES = ['/tests/', '/test/', '/androidTest/', '/perftests/', '/gts-tests/']
 SUBPATH_FOR_TEST_DATA_FILES = _FindFoldersContaining(git.repository_root(),
                                                      'IGNORE_CHECKSTYLE')
 ERROR_UNCOMMITTED = 'You need to commit all modified files before running Checkstyle\n'