Make "using namespace" a PRESUBMIT error.

Bug: 82078
Change-Id: Ibc9405d903008c5bebf04f558e1b2c42ba5ced4d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1879997Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Commit-Queue: Peter Kasting <pkasting@chromium.org>
Cr-Commit-Position: refs/heads/master@{#709655}

PRESUBMIT.py

@@ -500,6 +500,16 @@ _BANNED_CPP_FUNCTIONS = (
       False,
       (),
     ),
+    (
+      r'/\busing namespace ',
+      (
+       'Using directives ("using namespace x") are banned by the Google Style',
+       'Guide ( http://google.github.io/styleguide/cppguide.html#Namespaces ).',
+       'Explicitly qualify symbols or use using declarations ("using x::foo").',
+      ),
+      True,
+      [_THIRD_PARTY_EXCEPT_BLINK],  # Don't warn in third_party folders.
+    ),
     # Make sure that gtest's FRIEND_TEST() macro is not used; the
     # FRIEND_TEST_ALL_PREFIXES() macro from base/gtest_prod_util.h should be
     # used instead since that allows for FLAKY_ and DISABLED_ prefixes.

PRESUBMIT_test.py

@@ -1918,6 +1918,20 @@ class ServiceManifestOwnerTest(unittest.TestCase):
 
 class BannedTypeCheckTest(unittest.TestCase):
 
+  def testBannedCppFunctions(self):
+    input_api = MockInputApi()
+    input_api.files = [
+      MockFile('some/cpp/problematic/file.cc',
+               ['using namespace std;']),
+      MockFile('some/cpp/ok/file.cc',
+               ['using std::string;']),
+    ]
+
+    errors = PRESUBMIT._CheckNoBannedFunctions(input_api, MockOutputApi())
+    self.assertEqual(1, len(errors))
+    self.assertTrue('some/cpp/problematic/file.c' in errors[0].message)
+    self.assertTrue('some/cpp/ok/file.cc' not in errors[0].message)
+
   def testBannedIosObjcFunctions(self):
     input_api = MockInputApi()
     input_api.files = [