Update CheckNoContentUnitTestsInChrome presubmit check.

It should check BUILD.gn files instead of GYP files.

Change-Id: I83c9d454dd876ce1808dc7c3439b8c6238d4ebf9
Reviewed-on: https://chromium-review.googlesource.com/762150
Commit-Queue: Lei Zhang <thestig@chromium.org>
Reviewed-by: Jochen Eisinger <jochen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#515895}

chrome/PRESUBMIT.py

@@ -47,7 +47,7 @@ def _CheckNoContentUnitTestsInChrome(input_api, output_api):
   """Makes sure that no unit tests from content/ are included in unit_tests."""
   problems = []
   for f in input_api.AffectedFiles():
-    if not f.LocalPath().endswith('chrome_tests.gypi'):
+    if not f.LocalPath().endswith('BUILD.gn'):
       continue
 
     for line_num, line in f.ChangedContents():
@@ -59,7 +59,7 @@ def _CheckNoContentUnitTestsInChrome(input_api, output_api):
     return []
   return [output_api.PresubmitPromptWarning(
       'Unit tests located in content/ should be added to the ' +
-      'content_tests.gypi:content_unittests target.',
+      'content_unittests target.',
       items=problems)]