Add athena_strings.grd with athena specific strings

tools/check_grd_for_unused_strings.py

Index: tools/check_grd_for_unused_strings.py
diff --git a/tools/check_grd_for_unused_strings.py b/tools/check_grd_for_unused_strings.py
index 8124b57604a8e7709e43b0a41214529299ad6112..aa088f50533edce95e5972b398827bba720751d1 100755
--- a/tools/check_grd_for_unused_strings.py
+++ b/tools/check_grd_for_unused_strings.py
@@ -127,6 +127,7 @@ def main():
   # If no GRD files were given, default them:
   if len(grd_files) == 0:
     ash_base_dir = os.path.join(src_dir, 'ash')
+    athena_strings_dir = os.path.join(src_dir, 'athena', 'strings')
     chrome_dir = os.path.join(src_dir, 'chrome')
     chrome_app_dir = os.path.join(chrome_dir, 'app')
     chrome_app_res_dir = os.path.join(chrome_app_dir, 'resources')
@@ -137,6 +138,7 @@ def main():
     grd_files = [
       os.path.join(ash_base_dir, 'ash_strings.grd'),
       os.path.join(ash_base_dir, 'resources', 'ash_resources.grd'),
+      os.path.join(athena_strings_dir, 'athena_strings.grd'),
       os.path.join(chrome_app_dir, 'chromium_strings.grd'),
       os.path.join(chrome_app_dir, 'generated_resources.grd'),
       os.path.join(chrome_app_dir, 'google_chrome_strings.grd'),
@@ -165,6 +167,7 @@ def main():
     src_dirs = [
       os.path.join(src_dir, 'app'),
       os.path.join(src_dir, 'ash'),
+      os.path.join(src_dir, 'athena'),
       os.path.join(src_dir, 'chrome'),
       os.path.join(src_dir, 'components'),
       os.path.join(src_dir, 'content'),