A document's named getter collects elements with either matching name or
id's (varies per element type) and returns them .
We implement this the following way:
* Create an iterator with elements whose `name` attribute matches
* Create an iterator with elements whose `id` attribute matches
* Concatenate both
The spec then asks us if there is more than one element in the list,
which we implement by checking whether the iterator returns `None` after
we get the first element. However, the same element can appear in both
iterators if it is a `img` element and both it's name and id attribute
match. Therefore, we need to check if there are more elements *which are
not equal to the first one*.
Testing: New web platform tests pass
---------
Signed-off-by: Simon Wülker <simon.wuelker@arcor.de>
Most tests were only being run for layout-2013, not for layout-2020.
This wasn't great since layout-2020 is now the default.
So this patch unifies the lists of included tests for both layouts.
For layout-2013 this implies adding css/css-content/, css/css-logical/
and css/css-masking/clip/.
For layout-2020 this implies adding several additional css tests, and
also tests like dom/, js/, html/, etc.
