app_list: Exclude Objective-C from cpplint pass.

ui/app_list/PRESUBMIT.py

Index: ui/app_list/PRESUBMIT.py
diff --git a/ui/app_list/PRESUBMIT.py b/ui/app_list/PRESUBMIT.py
index 591fad1229fcb3f6207577c2f50d221257319237..0582ac4a071c5e3d38610d008994ffe6a3f05c08 100644
--- a/ui/app_list/PRESUBMIT.py
+++ b/ui/app_list/PRESUBMIT.py
@@ -7,14 +7,21 @@
 See http://dev.chromium.org/developers/how-tos/depottools/presubmit-scripts
 for more details about the presubmit API built into depot_tools.
 """
+
 INCLUDE_CPP_FILES_ONLY = (
-  r'.*\.cc$', r'.*\.h$'
+  r'.*\.(cc|h)$',
+)
+
+EXCLUDE = (
+  # Objective C confuses everything.
+  r'.*/cocoa/.*',
 )
 
 def CheckChangeLintsClean(input_api, output_api):
   """Makes sure that the ui/app_list/ code is cpplint clean."""
+  black_list = input_api.DEFAULT_BLACK_LIST + EXCLUDE
   sources = lambda x: input_api.FilterSourceFile(
-    x, white_list = INCLUDE_CPP_FILES_ONLY, black_list = None)
+    x, white_list = INCLUDE_CPP_FILES_ONLY, black_list = black_list)
   return input_api.canned_checks.CheckChangeLintsClean(
       input_api, output_api, sources)