Bug
1865172 Part 1 - Always store a page name value when a breakpoint is first found during block reflow. r=dholbert
This happens in a similar location to where we find a breakpoint caused by a
change in page name. However, if the breakpoint was caused by something else,
we still need to compute this value so that the next page being constructed
will have the correct page name.
This also "fixes" the WPT /css/printing/page-name-007-print.html, which passed
before this patch just because our previous logic would continue using the last
page value in those cases, which coincidentally matched what was expected.
Part 2 will include a test that specifically detects this discrepency.
Differential Revision: https://phabricator.services.mozilla.com/
D196895