W3C test import script prefixes some properties that it shouldn't

W3C test import script prefixes some properties that it shouldn't
https://bugs.webkit.org/show_bug.cgi?id=119357

Reviewed by Dirk Pranke.

Some prefixed properties also have unprefixed implemetations, but when
the implementations aren't identical, they aren't declared in
CSSPropertyNames.in on the same line. This fixes the import script so
that it catches all instances of prefixed properties that have an
unprefixed variant, and does not add the prefix in those cases.

* Scripts/webkitpy/w3c/test_converter.py:
(W3CTestConverter.read_webkit_prefixed_css_property_list): Read all of
the properties on every line and record if they are prefixed or not.
Use this information to only return prefixed properties that do not
have any unprefixed variant. The prefixed property list has also
changed to not include the '-webkit-' prefix, making it much easier to
do the comparison, and removing the need to remove the prefix later.
(W3CTestConverter.add_webkit_prefix_to_unprefixed_properties): This no
longer needs to remove the '-webkit-' prefix, but needs to add it in
the case where a property that needs a prefix is found.
* Scripts/webkitpy/w3c/test_converter_unittest.py:
(W3CTestConverterTest.test_read_prefixed_property_list): Remove assert
for '-webkit-' prefix, as it is no longer included in the properties
in the prefixed property list.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@153550 268f45cc-cd09-0410-ab3c-d52691b4dbfc