Enforce GN formatting for *.typemap files.

Ensure consistent formatting for Mojo typemap files that define the
build rules to generate StructTraits.

BUG=620799
TEST=Tested locally, both presubmit and git cl format work as expected.

Review-Url: https://codereview.chromium.org/2074793002

git_cl.py

@@ -4778,7 +4778,7 @@ def MatchingFileType(file_name, extensions):
 def CMDformat(parser, args):
   """Runs auto-formatting tools (clang-format etc.) on the diff."""
   CLANG_EXTS = ['.cc', '.cpp', '.h', '.mm', '.proto', '.java']
-  GN_EXTS = ['.gn', '.gni']
+  GN_EXTS = ['.gn', '.gni', '.typemap']
   parser.add_option('--full', action='store_true',
                     help='Reformat the full content of all touched files')
   parser.add_option('--dry-run', action='store_true',

presubmit_canned_checks.py

@@ -1170,7 +1170,8 @@ def CheckGNFormatted(input_api, output_api):
   affected_files = input_api.AffectedFiles(
       include_deletes=False,
       file_filter=lambda x: x.LocalPath().endswith('.gn') or
-                            x.LocalPath().endswith('.gni'))
+                            x.LocalPath().endswith('.gni') or
+                            x.LocalPath().endswith('.typemap'))
   warnings = []
   for f in affected_files:
     cmd = ['gn', 'format', '--dry-run', f.AbsoluteLocalPath()]