[LayoutNG] Handle unset column balancing results correctly.

Handle situations where nobody propagates "tallest unbreakable or
"minimal space shortage" to a fragment builder. This happens for
childless and/or monolithic content.

Simplify the DCHECKing for this mechanism, and make it return the
correct values, if nobody has set them.

We used to fail a DCHECK in TallestUnbreakableBlockSize() (called from
NGBoxFragmentBuilder::PropagateBreak()), and we would also return the
incorrect tallest_unbreakable_block_size if it was unset (it was
initialized to LayoutUnit::Max()).

Bug: 829028
Change-Id: Icaf3da7ad3b61b2a317f39dbc470a2512f9f992e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2404581
Commit-Queue: Morten Stenshorne <mstensho@chromium.org>
Reviewed-by: Ian Kilpatrick <ikilpatrick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#806210}

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

@@ -76,14 +76,11 @@ NGLayoutResult::NGLayoutResult(
     if (builder->tallest_unbreakable_block_size_ >= LayoutUnit()) {
       rare_data->tallest_unbreakable_block_size =
           builder->tallest_unbreakable_block_size_;
-#if DCHECK_IS_ON()
-      rare_data->has_tallest_unbreakable_block_size = true;
-#endif
-    }
-    if (builder->minimal_space_shortage_ != LayoutUnit::Max()) {
-#if DCHECK_IS_ON()
-      DCHECK(!rare_data->has_tallest_unbreakable_block_size);
-#endif
+
+      // This field shares storage with "minimal space shortage", so both
+      // cannot be set at the same time.
+      DCHECK_EQ(builder->minimal_space_shortage_, LayoutUnit::Max());
+    } else if (builder->minimal_space_shortage_ != LayoutUnit::Max()) {
       rare_data->minimal_space_shortage = builder->minimal_space_shortage_;
     }
 

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

@@ -185,22 +185,15 @@ class CORE_EXPORT NGLayoutResult : public RefCounted<NGLayoutResult> {
   }
 
   LayoutUnit MinimalSpaceShortage() const {
-    if (!HasRareData())
+    if (!HasRareData() || rare_data_->minimal_space_shortage == kIndefiniteSize)
       return LayoutUnit::Max();
-#if DCHECK_IS_ON()
-    // This field shares storage with another field.
-    DCHECK(!rare_data_->has_tallest_unbreakable_block_size);
-#endif
     return rare_data_->minimal_space_shortage;
   }
 
   LayoutUnit TallestUnbreakableBlockSize() const {
-    if (!HasRareData())
+    if (!HasRareData() ||
+        rare_data_->tallest_unbreakable_block_size == kIndefiniteSize)
       return LayoutUnit();
-#if DCHECK_IS_ON()
-    // This field shares storage with another field.
-    DCHECK(rare_data_->has_tallest_unbreakable_block_size);
-#endif
     return rare_data_->tallest_unbreakable_block_size;
   }
 
@@ -400,7 +393,7 @@ class CORE_EXPORT NGLayoutResult : public RefCounted<NGLayoutResult> {
       // couldn't fit all the content, and we're allowed to stretch columns
       // further, we'll perform another pass with the column block-size
       // increased by this amount.
-      LayoutUnit minimal_space_shortage = LayoutUnit::Max();
+      LayoutUnit minimal_space_shortage = kIndefiniteSize;
     };
     NGExclusionSpace exclusion_space;
     scoped_refptr<SerializedScriptValue> custom_layout_data;
@@ -408,10 +401,6 @@ class CORE_EXPORT NGLayoutResult : public RefCounted<NGLayoutResult> {
     LayoutUnit overflow_block_size = kIndefiniteSize;
     LayoutUnit annotation_overflow;
     LayoutUnit block_end_annotation_space;
-
-#if DCHECK_IS_ON()
-    bool has_tallest_unbreakable_block_size = false;
-#endif
     bool is_single_use = false;
     int lines_until_clamp = 0;
     wtf_size_t table_column_count_ = 0;

third_party/blink/web_tests/TestExpectations

@@ -1014,8 +1014,6 @@ crbug.com/829028 virtual/layout_ng_block_frag/external/wpt/css/css-break/fieldse
 crbug.com/1066380 virtual/layout_ng_block_frag/external/wpt/css/css-break/widows-orphans-002.html [ Failure ]
 crbug.com/1066380 virtual/layout_ng_block_frag/external/wpt/css/css-break/widows-orphans-004.html [ Failure ]
 crbug.com/829028 virtual/layout_ng_block_frag/external/wpt/css/css-break/widows-orphans-005.html [ Failure ]
-crbug.com/829028 virtual/layout_ng_block_frag/external/wpt/css/css-contain/contain-size-breaks-001.html [ Crash Failure ]
-crbug.com/829028 virtual/layout_ng_block_frag/external/wpt/css/css-contain/contain-size-monolithic-001.html [ Crash Failure ]
 crbug.com/829028 virtual/layout_ng_block_frag/external/wpt/css/css-contain/contain-size-multicol-001.html [ Failure ]
 crbug.com/1079031 virtual/layout_ng_block_frag/external/wpt/css/css-multicol/change-out-of-flow-type-and-remove-inner-multicol-crash.html [ Crash Failure ]
 crbug.com/1058792 virtual/layout_ng_block_frag/external/wpt/css/css-multicol/composited-under-clip-under-multicol.html [ Failure Crash ]