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

tools/metrics/histograms/PRESUBMIT.py

Index: tools/metrics/histograms/PRESUBMIT.py
diff --git a/tools/metrics/histograms/PRESUBMIT.py b/tools/metrics/histograms/PRESUBMIT.py
index a4b4ee74b0324673696dccdbe274837ef5280294..131fb8c4635f728dfa297a2eb545ca5e86de657e 100644
--- a/tools/metrics/histograms/PRESUBMIT.py
+++ b/tools/metrics/histograms/PRESUBMIT.py
@@ -28,6 +28,25 @@ def CheckChange(input_api, output_api):
         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 []