Collect UMA statistics on which chrome://flags lead to chrome restart on ChromeOS.

tools/metrics/histograms/PRESUBMIT.py

 # Copyright 2013 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.
 
 """
 See http://dev.chromium.org/developers/how-tos/depottools/presubmit-scripts
 for more details on the presubmit API built into gcl.
 """
 
 
@@ skipping 10 matching lines @@
         return [output_api.PresubmitError(
             'histograms.xml is not formatted correctly; run pretty_print.py '
             'to fix')]
 
       exit_code = input_api.subprocess.call(
           ['python', 'validate_format.py'], cwd=cwd)
       if exit_code != 0:
         return [output_api.PresubmitError(
             'histograms.xml is not well formatted; run validate_format.py '
             'and fix the reported errors')]
+
+      input_api.logging.info("Running LoginCustomFlagsChecker")
+      import sys
+      original_sys_path = sys.path
+
+      try:
+        sys.path.append(input_api.os_path.join(
+            input_api.PresubmitLocalPath(), cwd))
+        from verify_enum_custom_flags import LoginCustomFlagsChecker
+      finally:
+        sys.path = original_sys_path
+
+      histograms_file = input_api.os_path.join(
+          input_api.os_path.dirname(input_api.os_path.realpath("__file__")),
+                                    "histograms.xml")
+
+      return LoginCustomFlagsChecker(input_api, output_api,
+          path=histograms_file).Run()
+
   return []
 
 
 def CheckChangeOnUpload(input_api, output_api):
   return CheckChange(input_api, output_api)
 
 
 def CheckChangeOnCommit(input_api, output_api):
   return CheckChange(input_api, output_api)