Improve containing block creation for position:absolute flows

Instead of only promoting flows with positioned fragments to containing
blocks, also do this for flows which have the transform, perspective or
filter properties set. This is what the spec requires and also fixes
some failing tests. It will allow us to stop creating stacking contexts
for overflow:hidden and overflow:scroll flows.

Fixes #18091.

1 files changed, 8 insertions, 0 deletions

diff --git a/components/layout/table_caption.rs b/components/layout/table_caption.rs
index 6fc188ce71a..8e5fa302028 100644
--- a/components/layout/table_caption.rs
+++ b/components/layout/table_caption.rs
@@ -91,6 +91,14 @@ impl Flow for TableCaptionFlow {
         self.block_flow.compute_overflow()
     }
 
+    fn contains_roots_of_absolute_flow_tree(&self) -> bool {
+        self.block_flow.contains_roots_of_absolute_flow_tree()
+    }
+
+    fn is_absolute_containing_block(&self) -> bool {
+        self.block_flow.is_absolute_containing_block()
+    }
+
     fn generated_containing_block_size(&self, flow: OpaqueFlow) -> LogicalSize<Au> {
         self.block_flow.generated_containing_block_size(flow)
     }