[LayoutNG] Don't break inside monolithic block nodes.

We were already preventing breaks inside line boxes, but we also need to
do the same for certain types of block nodes, such as replaced content.

Add a unit test for break-before:avoid before monolithic block level
content, since the existing web_tests corpus has no break-between
avoidance tests at all.

Bug: 829028
Change-Id: I2240f96714e6dd760fac4f86089a0c8e6bf346ac
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1836492
Commit-Queue: Ian Kilpatrick <ikilpatrick@chromium.org>
Reviewed-by: Ian Kilpatrick <ikilpatrick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#702465}

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

@@ -2103,8 +2103,9 @@ NGBlockLayoutAlgorithm::BreakBeforeChildIfNeeded(
   } else {
     LayoutUnit space_left = FragmentainerSpaceAvailable() - block_offset;
     bool want_break;
-    if (child.IsInline()) {
-      // If the line doesn't fit, we need a break.
+    if (child.IsMonolithic()) {
+      // If the monolithic piece of content (e.g. a line, or block-level
+      // replaced content) doesn't fit, we need a break.
       NGFragment fragment(ConstraintSpace().GetWritingMode(),
                           physical_fragment);
       want_break = fragment.BlockSize() > space_left;

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

@@ -5087,5 +5087,40 @@ TEST_F(NGColumnLayoutAlgorithmTest, AvoidBreakBetweenBreakAtEarlyClassC) {
   EXPECT_EQ(expectation, dump);
 }
 
+TEST_F(NGColumnLayoutAlgorithmTest, AvoidBreakBeforeBlockReplacedContent) {
+  // Replaced content is unbreakable. Don't break right before it if we have
+  // break-before:avoid, though.
+  SetBodyInnerHTML(R"HTML(
+    <style>
+      #parent {
+        columns: 3;
+        column-gap: 10px;
+        column-fill: auto;
+        width: 320px;
+        height: 100px;
+      }
+    </style>
+    <div id="container">
+      <div id="parent">
+        <div style="width:22px; height:40px;"></div>
+        <div style="width:33px; height:50px; break-inside:avoid;"></div>
+        <img style="break-before:avoid; display:block; width:44px; height:50px;">
+      </div>
+    </div>
+  )HTML");
+
+  String dump = DumpFragmentTree(GetElementById("container"));
+  String expectation = R"DUMP(.:: LayoutNG Physical Fragment Tree ::.
+  offset:unplaced size:1000x100
+    offset:0,0 size:320x100
+      offset:0,0 size:100x100
+        offset:0,0 size:22x40
+      offset:110,0 size:100x100
+        offset:0,0 size:33x50
+        offset:0,50 size:44x50
+)DUMP";
+  EXPECT_EQ(expectation, dump);
+}
+
 }  // anonymous namespace
 }  // namespace blink

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

@@ -134,6 +134,14 @@ class CORE_EXPORT NGLayoutInputNode {
            (box_->IsBody() || box_->IsTableCell());
   }
 
+  // Return true if this node is monolithic for block fragmentation.
+  bool IsMonolithic() const {
+    // Lines are always monolithic. We cannot block-fragment inside them.
+    if (IsInline())
+      return true;
+    return box_->GetPaginationBreakability() == LayoutBox::kForbidBreaks;
+  }
+
   bool CreatesNewFormattingContext() const {
     return IsBlock() && box_->CreatesNewFormattingContext();
   }

third_party/blink/web_tests/TestExpectations

@@ -1648,7 +1648,6 @@ crbug.com/591099 virtual/layout_ng_experimental/fast/multicol/nested-with-single
 crbug.com/591099 virtual/layout_ng_experimental/fast/multicol/newmulticol/avoid-column-break-inside.html [ Failure ]
 crbug.com/591099 virtual/layout_ng_experimental/fast/multicol/newmulticol/balance2.html [ Failure ]
 crbug.com/591099 virtual/layout_ng_experimental/fast/multicol/newmulticol/balance3.html [ Failure ]
-crbug.com/591099 virtual/layout_ng_experimental/fast/multicol/newmulticol/balance-images.html [ Failure ]
 crbug.com/591099 virtual/layout_ng_experimental/fast/multicol/newmulticol/break-before.html [ Failure ]
 crbug.com/874506 virtual/layout_ng_experimental/fast/multicol/newmulticol/breaks-2-columns-3.html [ Failure ]
 crbug.com/591099 virtual/layout_ng_experimental/fast/multicol/newmulticol/breaks-2-columns-3-no-balancing.html [ Failure ]
@@ -1670,7 +1669,6 @@ crbug.com/591099 virtual/layout_ng_experimental/fast/multicol/overflow-across-co
 crbug.com/591099 virtual/layout_ng_experimental/fast/multicol/overflow-content.html [ Failure ]
 crbug.com/591099 virtual/layout_ng_experimental/fast/multicol/overflow-unsplittable.html [ Failure ]
 crbug.com/591099 virtual/layout_ng_experimental/fast/multicol/pageLogicalOffset-vertical.html [ Failure ]
-crbug.com/591099 virtual/layout_ng_experimental/fast/multicol/paginate-block-replaced.html [ Failure ]
 crbug.com/591099 virtual/layout_ng_experimental/fast/multicol/positioned-outside-of-columns.html [ Crash Failure ]
 crbug.com/591099 virtual/layout_ng_experimental/fast/multicol/positioned-split.html [ Failure ]
 crbug.com/591099 virtual/layout_ng_experimental/fast/multicol/positive-leading.html [ Failure ]
@@ -1817,7 +1815,6 @@ crbug.com/591099 virtual/layout_ng_experimental/fragmentation/float-after-forced
 crbug.com/591099 virtual/layout_ng_experimental/fragmentation/float-margin-top.html [ Failure ]
 crbug.com/591099 virtual/layout_ng_experimental/fragmentation/float-pushed-to-next-fragmentainer-by-floats.html [ Failure ]
 crbug.com/591099 virtual/layout_ng_experimental/fragmentation/forced-break-clearance-unsplittable-content.html [ Failure ]
-crbug.com/591099 virtual/layout_ng_experimental/fragmentation/image-block-as-first-child.html [ Failure ]
 crbug.com/591099 virtual/layout_ng_experimental/fragmentation/overflow-crossing-boundary.html [ Failure ]
 crbug.com/591099 virtual/layout_ng_experimental/fragmentation/relayout-abspos.html [ Failure ]
 crbug.com/591099 virtual/layout_ng_experimental/fragmentation/remove-unbreakable-block-in-line-float.html [ Failure ]