[css-text-3] New test with line-break / word-break / lang combinations

[faceless2]

No description provided.

[foolip]

@faceless2 in case you're wondering, the reason that this PR has a pending Taskcluster status is because that requirement was added after this PR was created. When you want to pick up work on this PR again, please rebase it on master and all the right checks should run. (I tried to do it for you, but didn't have permission to push to your branch.)

[foolip]

@frivoal were you going to review this?

[frivoal]

Finally made it to the top of the todo list :) sorry for the delay.

This is an interesting test, but it needs a few tweaks before we can take it in:

• please move it to one of the subdirectories of wpt/css/css-text. wpt/css/css-text/line-breaking seems appropriate
• Please add a descriptive sentence at the top, so that someone looking at it knows what they should expect. Something like

  <p>Test passes if the black and blue text in each pair of boxes is identical.

• This should be turned into a ref test
• The automated screenshot tool cannot (reliably) work with tests bigger than 800x600, but this is larger. Suggestion:
  • split into several files
  • turn the descriptive line at the beginning of each section into a html comment, to preserve it but hide if from the output
• Much of UAX14 is described as "tailorable", which is more RFC2119 "should" territory than "must". Tests for that sort of statements should have <meta name="flags" content="should">. This may be a good way to decide how to split the test into smaller files: put all the UAX14 non-tailorable requirements (such as the GL class) as well as all things directly required by css-text in some files, and all the rest (tailorable things) in other files, with the "should" meta tag.

[frivoal]

see #10420 (comment)