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

chrome/browser/PRESUBMIT.py

Index: chrome/browser/PRESUBMIT.py
diff --git a/chrome/browser/PRESUBMIT.py b/chrome/browser/PRESUBMIT.py
index a485728b350aa88c98b2728adc8330d729bca405..114b9c8c5152705be6b8bad295102fb0373bc80a 100644
--- a/chrome/browser/PRESUBMIT.py
+++ b/chrome/browser/PRESUBMIT.py
@@ -20,6 +20,22 @@ def CheckChangeOnUpload(input_api, output_api):
 def CheckChangeOnCommit(input_api, output_api):
   return _CommonChecks(input_api, output_api)
 
+# chrome/browser/about_flags_switches_histogram_ids.h
+def _CreateAboutFlagsSwitchesHistogramIdsChecker(input_api, output_api):
+  import sys
+  original_sys_path = sys.path
+
+  try:
+    sys.path.append(input_api.os_path.join(
+        input_api.PresubmitLocalPath(), '..', '..', 'tools',
+        'about_flags_switches_histogram_ids_checker'))
+    from about_flags_switches_histogram_ids_checker \
+        import AboutFlagsSwitchesHistogramIDsChecker
+  finally:
+    sys.path = original_sys_path
+
+  return AboutFlagsSwitchesHistogramIDsChecker(input_api, output_api,
+      path='chrome/browser/about_flags_switches_histogram_ids.h')
 
 def _CommonChecks(input_api, output_api):
   """Checks common to both upload and commit."""
@@ -66,4 +82,10 @@ def _CommonChecks(input_api, output_api):
   finally:
     sys.path = old_path
 
+  affected_files = (f.AbsoluteLocalPath() for f in input_api.AffectedFiles())
+  if path.join(cwd, 'about_flags_switches_histogram_ids.h') in affected_files :
+    input_api.logging.info("Running AboutFlagsSwitchesHistogramIdsChecker.")
+    results += _CreateAboutFlagsSwitchesHistogramIdsChecker(input_api,
+                                                            output_api).Run()
+
   return results