Add presubmit scripts to check histograms.xml if bad_message.h changes.

tools/metrics/histograms/presubmit_bad_message_reasons.py

Index: tools/metrics/histograms/presubmit_bad_message_reasons.py
diff --git a/tools/metrics/histograms/presubmit_bad_message_reasons.py b/tools/metrics/histograms/presubmit_bad_message_reasons.py
new file mode 100644
index 0000000000000000000000000000000000000000..0548607b15c85adf078fbde4dfaacb472386a25c
--- /dev/null
+++ b/tools/metrics/histograms/presubmit_bad_message_reasons.py
@@ -0,0 +1,38 @@
+# Copyright 2017 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.
+
+"""Check to see if the various BadMessage enums in histograms.xml need to be
+updated. This can be called from a chromium PRESUBMIT.py to ensure updates to
+bad_message.h also include the generated changes to histograms.xml
+"""
+
+import update_histogram_enum
+
+def PrecheckBadMessage(input_api, output_api, histogram_name):
+  source_path = ''
+
+  # This function is called once per bad_message.h-containing directory. Check
+  # for the |bad_message.h| file, and if present, remember its path.
+  for f in input_api.AffectedFiles():
+    if f.LocalPath().endswith('bad_message.h'):
+      source_path = f.LocalPath()
+      break
+
+  # If the |bad_message.h| wasn't found in this change, then there is nothing to
+  # do and histogram.xml does not need to be updated.
+  if source_path == '':
+    return []
+
+  START_MARKER='^enum (class )?BadMessageReason {'
+  END_MARKER='^BAD_MESSAGE_MAX'
+  if update_histogram_enum.HistogramNeedsUpdate(
+      histogram_enum_name=histogram_name,
+      source_enum_path=source_path,
+      start_marker=START_MARKER,
+      end_marker=END_MARKER):
+    return [output_api.PresubmitPromptWarning(
+        'bad_messages.h has been updated but histogram.xml does not '
+        'appear to be updated.\nPlease run:\n'
+        '  python tools/metrics/histograms/update_bad_message_reasons.py\n')]
+  return []