Instead of rendering a reference HTML page that wraps an <img> tag
pointing to a PNG, Screenshot tests now load the expected PNG directly
from disk and compare it against the rendered screenshot. This
eliminates the indirection of loading and rendering a second page just
to display a static image.
This also means --rebaseline now works for Screenshot tests, generating
the expected PNG automatically instead of requiring manual screenshot
capture and placement.
Changes:
- Add TestMode::Screenshot with its own collector and runner
- Move PNGs from Screenshot/images/ to Screenshot/expected/ with
normalized names matching input filenames
- Remove all 92 reference HTML wrapper files and the images/
directory
- Remove <link rel="match"> from all 94 Screenshot input HTML
files
- Update add_libweb_test.py Screenshot boilerplate accordingly
- Add Screenshot mode to results viewer image comparison tabs
Steps 4 and 5 were swapped since marking all the nodes between the start
and end of the selection now also marks the end node as full, even if it
should be marked as End.
There could be extra logic to avoid marking it if it is a text node, but
this seems easier.
As a whole, this fixes partially selected non-text nodes. In such cases,
where the selection starts or ends inside a node with descendants, it is
impossible to just select from the start node to the end node since that
would select all descendants of the start node and none of the end node.
Previously, this was only half considered and only if the start node was
a descendant of the end node.
