Improve json_comment_eater.py performance.

PRESUBMIT.py

 # Copyright (c) 2012 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.
 
 """Top-level presubmit script for Chromium.
 
 See http://dev.chromium.org/developers/how-tos/depottools/presubmit-scripts
 for more details about the presubmit API built into depot_tools.
 """
 
@@ skipping 1395 matching lines @@
 def _CheckParseErrors(input_api, output_api):
   """Check that IDL and JSON files do not contain syntax errors."""
   actions = {
     '.idl': _GetIDLParseError,
     '.json': _GetJSONParseError,
   }
   # These paths contain test data and other known invalid JSON files.
   excluded_patterns = [
     r'test[\\\/]data[\\\/]',
     r'^components[\\\/]policy[\\\/]resources[\\\/]policy_templates\.json$',
+    # Contains valid JSON but is excluded for performance reasons. The
+    # well-formedness of this file is checked during the build.
+    r'^net[\\\/]http[\\\/]transport_security_state_static\.json$',

[Dirk Pranke, 2017/04/10 19:34:27]

Seems like we should fix the comment eater instead, there must be a pathological
bug in the parser for it to be this slow.

However, I'm not really okay with checking things in that call themselves json
but aren't actually json, so theoretically these should be .json5 or something
else instead.

But either of those things are more work.

Can you file a bug to follow up on this and cc me on it?

[martijnc, 2017/04/11 20:18:13]

I've updated the CL to fix the performance issue instead.
Filed https://crbug.com/710587 for the incorrect extensions but I don't have
editbug privileges so I can't CC you.

   ]
   # Most JSON files are preprocessed and support comments, but these do not.
   json_no_comments_patterns = [
     r'^testing[\\\/]',
   ]
   # Only run IDL checker on files in these directories.
   idl_included_patterns = [
     r'^chrome[\\\/]common[\\\/]extensions[\\\/]api[\\\/]',
     r'^extensions[\\\/]common[\\\/]api[\\\/]',
   ]
@@ skipping 979 matching lines @@
       output_api,
       json_url='http://chromium-status.appspot.com/current?format=json'))
 
   results.extend(
       input_api.canned_checks.CheckPatchFormatted(input_api, output_api))
   results.extend(input_api.canned_checks.CheckChangeHasBugField(
       input_api, output_api))
   results.extend(input_api.canned_checks.CheckChangeHasDescription(
       input_api, output_api))
   return results