Auto merge of #18506 - mrobinson:position-sticky-table, r=emilio

Fix issues with the combination of position:sticky and tables

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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [ ] These changes fix #18441 (github issue number if applicable).

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- [ ] These changes do not require tests because _____

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1 files changed, 26 insertions, 19 deletions

diff --git a/components/layout/display_list_builder.rs b/components/layout/display_list_builder.rs
index 9c0d6449164..80665f4acbf 100644
--- a/components/layout/display_list_builder.rs
+++ b/components/layout/display_list_builder.rs
@@ -103,11 +103,10 @@ fn convert_repeat_mode(from: RepeatKeyword) -> RepeatMode {
     }
 }
 
-fn establishes_containing_block_for_absolute(can_establish_containing_block: EstablishContainingBlock,
+fn establishes_containing_block_for_absolute(flags: StackingContextCollectionFlags,
                                              positioning: position::T)
                                              -> bool {
-    can_establish_containing_block == EstablishContainingBlock::Yes &&
-    position::T::static_ != positioning
+    !flags.contains(NEVER_CREATES_CONTAINING_BLOCK) && position::T::static_ != positioning
 }
 
 trait RgbColor {
@@ -2346,16 +2345,19 @@ impl FragmentDisplayListBuilding for Fragment {
     }
 }
 
-#[derive(Clone, Copy, PartialEq)]
-pub enum EstablishContainingBlock {
-    Yes,
-    No,
+bitflags! {
+    pub flags StackingContextCollectionFlags: u8 {
+        /// This flow never establishes a containing block.
+        const NEVER_CREATES_CONTAINING_BLOCK = 0x01,
+        /// This flow never creates a ClipScrollNode.
+        const NEVER_CREATES_CLIP_SCROLL_NODE = 0x02,
+    }
 }
 
 pub trait BlockFlowDisplayListBuilding {
     fn collect_stacking_contexts_for_block(&mut self,
                                            state: &mut StackingContextCollectionState,
-                                           can_establish_containing_block: EstablishContainingBlock);
+                                           flags: StackingContextCollectionFlags);
 
     fn transform_clip_to_coordinate_space(&mut self,
                                           state: &mut StackingContextCollectionState,
@@ -2364,7 +2366,7 @@ pub trait BlockFlowDisplayListBuilding {
                                 state: &mut StackingContextCollectionState,
                                 preserved_state: &mut SavedStackingContextCollectionState,
                                 stacking_context_type: BlockStackingContextType,
-                                can_establish_containing_block: EstablishContainingBlock)
+                                flags: StackingContextCollectionFlags)
                                 -> ClipAndScrollInfo;
     fn setup_clip_scroll_node_for_position(&mut self,
                                            state: &mut StackingContextCollectionState,
@@ -2521,7 +2523,7 @@ impl BlockFlowDisplayListBuilding for BlockFlow {
 
     fn collect_stacking_contexts_for_block(&mut self,
                                            state: &mut StackingContextCollectionState,
-                                           can_establish_containing_block: EstablishContainingBlock) {
+                                           flags: StackingContextCollectionFlags) {
         let mut preserved_state = SavedStackingContextCollectionState::new(state);
 
         let block_stacking_context_type = self.block_stacking_context_type();
@@ -2544,10 +2546,9 @@ impl BlockFlowDisplayListBuilding for BlockFlow {
             self.setup_clipping_for_block(state,
                                           &mut preserved_state,
                                           block_stacking_context_type,
-                                          can_establish_containing_block);
+                                          flags);
 
-        if establishes_containing_block_for_absolute(can_establish_containing_block,
-                                                     self.positioning()) {
+        if establishes_containing_block_for_absolute(flags, self.positioning()) {
             state.containing_block_clip_and_scroll_info = state.current_clip_and_scroll_info;
         }
 
@@ -2574,7 +2575,7 @@ impl BlockFlowDisplayListBuilding for BlockFlow {
                                 state: &mut StackingContextCollectionState,
                                 preserved_state: &mut SavedStackingContextCollectionState,
                                 stacking_context_type: BlockStackingContextType,
-                                can_establish_containing_block: EstablishContainingBlock)
+                                flags: StackingContextCollectionFlags)
                                 -> ClipAndScrollInfo {
         // If this block is absolutely positioned, we should be clipped and positioned by
         // the scroll root of our nearest ancestor that establishes a containing block.
@@ -2602,14 +2603,17 @@ impl BlockFlowDisplayListBuilding for BlockFlow {
             self.transform_clip_to_coordinate_space(state, preserved_state);
         }
 
-        self.setup_clip_scroll_node_for_position(state, &stacking_relative_border_box);
-        self.setup_clip_scroll_node_for_overflow(state, &stacking_relative_border_box);
-        self.setup_clip_scroll_node_for_css_clip(state, preserved_state, &stacking_relative_border_box);
+        if !flags.contains(NEVER_CREATES_CLIP_SCROLL_NODE) {
+            self.setup_clip_scroll_node_for_position(state, &stacking_relative_border_box);
+            self.setup_clip_scroll_node_for_overflow(state, &stacking_relative_border_box);
+            self.setup_clip_scroll_node_for_css_clip(state, preserved_state,
+                                                     &stacking_relative_border_box);
+        }
         self.base.clip = state.clip_stack.last().cloned().unwrap_or_else(max_rect);
 
         // We keep track of our position so that any stickily positioned elements can
         // properly determine the extent of their movement relative to scrolling containers.
-        if can_establish_containing_block == EstablishContainingBlock::Yes {
+        if !flags.contains(NEVER_CREATES_CONTAINING_BLOCK) {
             let border_box = if self.fragment.establishes_stacking_context() {
                 stacking_relative_border_box
             } else {
@@ -2678,6 +2682,9 @@ impl BlockFlowDisplayListBuilding for BlockFlow {
 
         let new_clip_scroll_node_id = ClipId::new(self.fragment.unique_id(IdType::OverflowClip),
                                                   state.pipeline_id.to_webrender());
+        if state.has_clip_scroll_node(new_clip_scroll_node_id) {
+             return;
+        }
         let parent_id = self.clip_and_scroll_info(state.pipeline_id).scroll_node_id;
         state.add_clip_scroll_node(
             ClipScrollNode {
@@ -2928,7 +2935,7 @@ impl InlineFlowDisplayListBuilding for InlineFlow {
 
         for fragment in self.fragments.fragments.iter_mut() {
             let previous_cb_clip_scroll_info = state.containing_block_clip_and_scroll_info;
-            if establishes_containing_block_for_absolute(EstablishContainingBlock::Yes,
+            if establishes_containing_block_for_absolute(StackingContextCollectionFlags::empty(),
                                                          fragment.style.get_box().position) {
                 state.containing_block_clip_and_scroll_info = state.current_clip_and_scroll_info;
             }