name_style_converter: Define __hash__() method

__hash__() isn't defined by default in Python 3 if __eq__() is
user-defined.
This fixes NameStyleConverter being unhashable in Python 3.

The default __hash__() in Python 2 is defined in terms of id(self),
i.e. identity-based hashing.
However, since the custom __eq__() is defined in terms of value
equality, this is probably unintended and a bug.
Thus this CL also changes behaviour by defining __hash__() in terms of
hash(self.original), i.e. value-based hashing.

Traceback (most recent call last):
  File "../../third_party/blink/renderer/build/scripts/make_feature_policy_helper.py", line 80, in <module>
    json5_generator.Maker(FeaturePolicyFeatureWriter).main()
  File "C:\Google\chromium\src\third_party\blink\renderer\build\scripts\json5_generator.py", line 337, in main
    writer = self._writer_class(args.files, args.output_dir)
  File "../../third_party/blink/renderer/build/scripts/make_feature_policy_helper.py", line 44, in __init__
    fp_origin_trial_dependency_map[feature['name']].append(
TypeError: unhashable type: 'NameStyleConverter'

Bug: 941669
Change-Id: Ie7811c7a5e0620376bf01c0d91a2c14043c85293
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2093491
Commit-Queue: Raul Tambre <raul@tambre.ee>
Reviewed-by: Kent Tamura <tkent@chromium.org>
Auto-Submit: Raul Tambre <raul@tambre.ee>
Cr-Commit-Position: refs/heads/master@{#748123}

third_party/blink/renderer/build/scripts/blinkbuild/name_style_converter.py

@@ -134,6 +134,10 @@ class NameStyleConverter(object):
     def __eq__(self, other):
         return self.original == other.original
 
+    # If __eq__() is defined then a custom __hash__() needs to be defined.
+    def __hash__(self):
+        return hash(self.original)
+
     def to_snake_case(self):
         """Snake case is the file and variable name style per Google C++ Style
            Guide:

third_party/blink/renderer/build/scripts/blinkbuild/name_style_converter_test.py

@@ -200,5 +200,16 @@ class NameStyleConverterTest(unittest.TestCase):
         converter = NameStyleConverter('third_party/blink/renderer/bindings/modules/v8/v8_path_2d.h')
         self.assertEqual(converter.to_header_guard(), 'THIRD_PARTY_BLINK_RENDERER_BINDINGS_MODULES_V8_V8_PATH_2D_H_')
 
+    def test_equality(self):
+        a_1 = NameStyleConverter('a')
+        a_2 = NameStyleConverter('a')
+        c = NameStyleConverter('c')
+
+        self.assertEqual(a_1, a_2)
+        self.assertNotEqual(a_1, c)
+        self.assertEqual(hash(a_1), hash(a_2))
+        self.assertNotEqual(hash(a_1), hash(c))
+
+
 if __name__ == '__main__':
     unittest.main()