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

components/nacl/browser/PRESUBMIT.py

Index: components/nacl/browser/PRESUBMIT.py
diff --git a/components/nacl/browser/PRESUBMIT.py b/components/nacl/browser/PRESUBMIT.py
new file mode 100644
index 0000000000000000000000000000000000000000..900111a3197a4d16319920ad00fbac987c74c61a
--- /dev/null
+++ b/components/nacl/browser/PRESUBMIT.py
@@ -0,0 +1,26 @@
+# 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.
+"""Chromium presubmit script to check that BadMessage enums in histograms.xml

[brettw, 2017/02/01 00:28:22]

Can you put a blank line between the copyright and the docstring?

Same in the other files.

[dougt, 2017/02/01 02:49:06]

Done.

+match the corresponding bad_message.h file.
+"""
+
+def _RunHistogramChecks(input_api, output_api, histogram_name):
+  try:
+    # Setup sys.path so that we can call histrogram code
+    import sys
+    original_sys_path = sys.path
+    sys.path = sys.path + [input_api.os_path.join(
+      input_api.change.RepositoryRoot(),
+      'tools', 'metrics', 'histograms')]
+
+    import presubmit_bad_message_reasons
+    return presubmit_bad_message_reasons.PrecheckBadMessage(input_api,
+      output_api, histogram_name)
+  except:
+    return [output_api.PresubmitError('Could not verify histogram!')]
+  finally:
+    sys.path = original_sys_path
+
+def CheckChangeOnUpload(input_api, output_api):
+  return _RunHistogramChecks(input_api, output_api, "BadMessageReasonNaCl")