Auto merge of #18212 - mrobinson:position-sticky, r=emilio

Add support for position:sticky

This leverages the position:sticky support in WebRender to bring basic
support for position:sticky in Servo. There are still some issues with
nested sticky flows as well as a few other corner cases. Tests are
imported from WPT and can be removed once we update to the latest
version.

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- [ ] These changes fix #__ (github issue number if applicable).

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1 files changed, 3 insertions, 2 deletions

diff --git a/components/layout/table.rs b/components/layout/table.rs
index da129747da8..2659b260501 100644
--- a/components/layout/table.rs
+++ b/components/layout/table.rs
@@ -10,7 +10,8 @@ use app_units::Au;
 use block::{BlockFlow, CandidateBSizeIterator, ISizeAndMarginsComputer};
 use block::{ISizeConstraintInput, ISizeConstraintSolution};
 use context::LayoutContext;
-use display_list_builder::{BlockFlowDisplayListBuilding, BorderPaintingMode, DisplayListBuildState};
+use display_list_builder::{BlockFlowDisplayListBuilding, BorderPaintingMode};
+use display_list_builder::{DisplayListBuildState, EstablishContainingBlock};
 use euclid::Point2D;
 use flow;
 use flow::{BaseFlow, EarlyAbsolutePositionInfo, Flow, FlowClass, ImmutableFlowUtils, OpaqueFlow};
@@ -503,7 +504,7 @@ impl Flow for TableFlow {
     }
 
     fn collect_stacking_contexts(&mut self, state: &mut DisplayListBuildState) {
-        self.block_flow.collect_stacking_contexts(state);
+        self.block_flow.collect_stacking_contexts_for_block(state, EstablishContainingBlock::Yes);
     }
 
     fn repair_style(&mut self, new_style: &::ServoArc<ComputedValues>) {