[Closure Externs] Add more APIs to the presubmit warning list

extensions/common/api/externs_checker_test.py

 #!/usr/bin/env python
 # Copyright 2016 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import os
 import sys
 import unittest
 
 from externs_checker import ExternsChecker
 
 sys.path.append(
     os.path.join(os.path.dirname(os.path.abspath(__file__)), '..', '..', '..'))
 
 from PRESUBMIT_test_mocks import MockInputApi, MockOutputApi, MockFile
 
 
 class ExternsCheckerTest(unittest.TestCase):
   API_PAIRS = {'a': '1', 'b': '2', 'c': '3'}
 
-  def _runChecks(self, files):
+  def _runChecks(self, files, exists=lambda f: True):
     input_api = MockInputApi()
+    input_api.os_path.exists = exists
     input_api.files = [MockFile(f, '') for f in files]
     output_api = MockOutputApi()
     checker = ExternsChecker(input_api, output_api, self.API_PAIRS)
     return checker.RunChecks()
 
   def testModifiedSourceWithoutModifiedExtern(self):
     results = self._runChecks(['b', 'test', 'random'])
     self.assertEquals(1, len(results))
     self.assertEquals(1, len(results[0].items))
     self.assertEquals('b', results[0].items[0])
@@ skipping 18 matching lines @@
         ' src/ $ python tools/json_schema_compiler/compiler.py <source_file> '
         '--root=. --generator=externs > <output_file>',
         results[0].long_text)
 
   def testModifiedMultipleSourcesWithOneModifiedExtern(self):
     results = self._runChecks(['b', 'test', 'c', 'random', '2'])
     self.assertEquals(1, len(results))
     self.assertEquals(1, len(results[0].items))
     self.assertEquals('c', results[0].items[0])
 
+  def testApiFileDoesNotExist(self):
+    exists = lambda f: f in ['a', 'b', 'c', '1', '2']
+    with self.assertRaises(OSError) as e:
+      self._runChecks(['a'], exists)
+    self.assertEqual('Path Not Found: 3', str(e.exception))
+
 
 if __name__ == '__main__':
   unittest.main()