WIP: Add auto-sheriff.appspot.com code to Blink

Tools/AutoSheriff/string_helpers.py

Index: Tools/AutoSheriff/string_helpers.py
diff --git a/Tools/AutoSheriff/string_helpers.py b/Tools/AutoSheriff/string_helpers.py
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+# Copyright 2014 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.
+
+import itertools
+
+# http://stackoverflow.com/questions/9470611/how-to-do-an-inverse-range-i-e-create-a-compact-range-based-on-a-set-of-numb/9471386#9471386
+def re_range(lst):
+    def sub(x):
+        return x[1] - x[0]
+
+    ranges = []
+    for k, iterable in itertools.groupby(enumerate(sorted(lst)), sub):
+         rng = list(iterable)
+         if len(rng) == 1:
+             s = str(rng[0][1])
+         else:
+             s = "%s-%s" % (rng[0][1], rng[-1][1])
+         ranges.append(s)
+    return ', '.join(ranges)