[LayoutNG] Don't fragment monolithic content.

fragmentation/auto-overflow.html now starts to fail, but that test is
invalid, so removing it. A block with overflow:auto is potentially
scrollable, and treating it as monolithic therefore makes sense. All
other browsers do this as well. Note that we did actually "always" treat
it as monolithic, as far as LayoutBox::GetPaginationBreakability() was
concerned, but since our legacy engine doesn't really understand
fragmentation, we ended up slicing it, making the test pass. LayoutNG
will now let such tall objects overflow the column instead, which
wouldn't match the expectation.

Bug: 829028
Change-Id: Id2ca5488049ef8e768a363e4dbe8767c7bc4d645
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2062351Reviewed-by: Ian Kilpatrick <ikilpatrick@chromium.org>
Commit-Queue: Morten Stenshorne <mstensho@chromium.org>
Cr-Commit-Position: refs/heads/master@{#742541}

third_party/blink/renderer/core/layout/ng/ng_block_layout_algorithm.cc

@@ -2420,8 +2420,8 @@ NGConstraintSpace NGBlockLayoutAlgorithm::CreateConstraintSpaceForChild(
     // fragmentation line.
     if (is_new_fc)
       fragmentainer_offset_delta = *child_bfc_block_offset;
-    SetupFragmentation(ConstraintSpace(), fragmentainer_offset_delta, &builder,
-                       is_new_fc);
+    SetupFragmentation(ConstraintSpace(), child, fragmentainer_offset_delta,
+                       &builder, is_new_fc);
     builder.SetEarlyBreakAppeal(container_builder_.BreakAppeal());
   }
 

third_party/blink/renderer/core/layout/ng/ng_column_layout_algorithm.cc

@@ -659,7 +659,8 @@ NGBreakStatus NGColumnLayoutAlgorithm::LayoutSpanner(
   margin_strut->Append(margins.block_start, /* is_quirky */ false);
 
   LayoutUnit block_offset = intrinsic_block_size_ + margin_strut->Sum();
-  auto spanner_space = CreateConstraintSpaceForSpanner(block_offset);
+  auto spanner_space =
+      CreateConstraintSpaceForSpanner(spanner_node, block_offset);
 
   const NGEarlyBreak* early_break_in_child = nullptr;
   if (early_break_ && early_break_->Type() == NGEarlyBreak::kBlock &&
@@ -987,6 +988,7 @@ NGConstraintSpace NGColumnLayoutAlgorithm::CreateConstraintSpaceForBalancing(
 }
 
 NGConstraintSpace NGColumnLayoutAlgorithm::CreateConstraintSpaceForSpanner(
+    const NGBlockNode& spanner,
     LayoutUnit block_offset) const {
   NGConstraintSpaceBuilder space_builder(
       ConstraintSpace(), Style().GetWritingMode(), /* is_new_fc */ true);
@@ -994,7 +996,7 @@ NGConstraintSpace NGColumnLayoutAlgorithm::CreateConstraintSpaceForSpanner(
   space_builder.SetPercentageResolutionSize(content_box_size_);
 
   if (ConstraintSpace().HasBlockFragmentation()) {
-    SetupFragmentation(ConstraintSpace(), block_offset, &space_builder,
+    SetupFragmentation(ConstraintSpace(), spanner, block_offset, &space_builder,
                        /* is_new_fc */ true);
   }
 

third_party/blink/renderer/core/layout/ng/ng_column_layout_algorithm.h

@@ -91,6 +91,7 @@ class CORE_EXPORT NGColumnLayoutAlgorithm
   NGConstraintSpace CreateConstraintSpaceForBalancing(
       const LogicalSize& column_size) const;
   NGConstraintSpace CreateConstraintSpaceForSpanner(
+      const NGBlockNode& spanner,
       LayoutUnit block_offset) const;
   NGConstraintSpace CreateConstraintSpaceForMinMax() const;
 

third_party/blink/renderer/core/layout/ng/ng_floats_utils.cc

@@ -72,8 +72,8 @@ NGConstraintSpace CreateConstraintSpaceForFloat(
     DCHECK(parent_space.HasBlockFragmentation());
     DCHECK_EQ(style.GetWritingMode(), parent_space.GetWritingMode());
 
-    SetupFragmentation(parent_space, *origin_block_offset, &builder,
-                       /* is_new_fc */ true);
+    SetupFragmentation(parent_space, unpositioned_float.node,
+                       *origin_block_offset, &builder, /* is_new_fc */ true);
   } else {
     builder.SetFragmentationType(NGFragmentationType::kFragmentNone);
   }

third_party/blink/renderer/core/layout/ng/ng_fragmentation_utils.cc

@@ -164,11 +164,20 @@ NGBreakAppeal CalculateBreakAppealInside(const NGConstraintSpace& space,
 }
 
 void SetupFragmentation(const NGConstraintSpace& parent_space,
+                        const NGLayoutInputNode& child,
                         LayoutUnit fragmentainer_offset_delta,
                         NGConstraintSpaceBuilder* builder,
                         bool is_new_fc) {
   DCHECK(parent_space.HasBlockFragmentation());
 
+  // If the child is truly unbreakable, it won't participate in block
+  // fragmentation. If it's too tall to fit, it will either overflow the
+  // fragmentainer or get brutally sliced into pieces (without looking for
+  // allowed breakpoints, since there are none, by definition), depending on
+  // fragmentation type (multicol vs. printing).
+  if (child.IsMonolithic())
+    return;
+
   builder->SetFragmentainerBlockSize(parent_space.FragmentainerBlockSize());
   builder->SetFragmentainerOffsetAtBfc(parent_space.FragmentainerOffsetAtBfc() +
                                        fragmentainer_offset_delta);

third_party/blink/renderer/core/layout/ng/ng_fragmentation_utils.h

@@ -93,6 +93,7 @@ inline void AdjustForFragmentation(const NGBlockBreakToken* break_token,
 // formatting context starts in a previous fragmentainer; the offset from the
 // current fragmentainer block-start.
 void SetupFragmentation(const NGConstraintSpace& parent_space,
+                        const NGLayoutInputNode& child,
                         LayoutUnit fragmentainer_offset_delta,
                         NGConstraintSpaceBuilder*,
                         bool is_new_fc);

third_party/blink/web_tests/TestExpectations

@@ -1144,7 +1144,6 @@ crbug.com/994172 virtual/layout_ng_block_frag/fast/multicol/balance-line-underfl
 crbug.com/994172 virtual/layout_ng_block_frag/fast/multicol/balance-line-underflow-2.html [ Pass Crash ]
 crbug.com/591099 virtual/layout_ng_block_frag/fast/multicol/basic-rtl.html [ Failure ]
 crbug.com/591099 virtual/layout_ng_block_frag/fast/multicol/break-before-first-line-in-first-child.html [ Failure ]
-crbug.com/591099 virtual/layout_ng_block_frag/fast/multicol/break-in-scrollable.html [ Failure ]
 crbug.com/591099 virtual/layout_ng_block_frag/fast/multicol/caret-range-anonymous-block.html [ Failure ]
 crbug.com/591099 virtual/layout_ng_block_frag/fast/multicol/caret-range-anonymous-block-rtl.html [ Failure ]
 crbug.com/591099 virtual/layout_ng_block_frag/fast/multicol/caret-range-outside-columns.html [ Failure ]

third_party/blink/web_tests/fragmentation/auto-overflow-expected.html

-<!DOCTYPE html>
-<p>There should be a hotpink square below.</p>
-<div style="width:50px; height:50px; background:hotpink;"></div>

third_party/blink/web_tests/fragmentation/auto-overflow.html

-<!DOCTYPE html>
-<p>There should be a hotpink square below.</p>
-<div id="multicol" style="columns:3; column-fill:auto; column-gap:0; height:50px;">
-    <div style="overflow:auto; height:100px; background:hotpink;"></div>
-</div>
-<script>
-  document.body.offsetTop;
-  document.getElementById("multicol").style.width = "75px";
-</script>