Bug 1822118 - display: inline list-item is also a line participant. r=dshin

So the line break suppression flags should be propagated through it.

Otherwise ruby invariants might break, leading to a nullptr crash in
this case.

On debug builds the assertion was this one:

  https://searchfox.org/mozilla-central/rev/e6cb503ac22402421186e7488d4250cc1c5fecab/layout/generic/nsRubyBaseContainerFrame.cpp#631

Differential Revision: https://phabricator.services.mozilla.com/D177093

layout/generic/crashtests/1822118.html

@@ -0,0 +1,11 @@
+<style>
+.a {
+  min-width: 641em;
+  display: list-item inline;
+}
+</style>
+A
+<ruby>
+<rp class="a">
+<rt>
+<fieldset class="a">

layout/generic/crashtests/crashtests.list

@@ -817,4 +817,5 @@ load 1799749.html
 pref(layout.css.content-visibility.enabled,true) asserts(1-4) load 1807958.html # asserts from integer overflow & bogus sizes
 load 1816574.html
 load 1821603.html
+load 1822118.html
 load 1825434.html

servo/components/style/values/specified/box.rs

@@ -308,8 +308,10 @@ impl Display {
     /// participant, which means it may lay its children on the same
     /// line as itself.
     pub fn is_line_participant(&self) -> bool {
+        if self.is_inline_flow() {
+            return true;
+        }
         match *self {
-            Display::Inline => true,
             #[cfg(feature = "gecko")]
             Display::Contents | Display::Ruby | Display::RubyBaseContainer => true,
             _ => false,