[LayoutNG] Improved legacy write-back for multicol.

This fixes crashers in layout tests.

A recent change, probably
https://chromium-review.googlesource.com/c/chromium/src/+/912551
triggered a bunch of crashers in fast/multicol/ , because it calls
LayoutFlowThread::PageRemainingLogicalHeightForOffset(), which DCHECKs
on IsPageLogicalHeightKnown(). So have NG mark logical height as known,
to avoid the DCHECK failure.

In addition to fixing those 91 new crashers (note that the test
expectation file hadn't been updated to expect crashers for those), this
also fixes some old crashers. Most of them go from Crash to Failure, but
a few even pass now.

Cq-Include-Trybots: master.tryserver.chromium.linux:linux_layout_tests_layout_ng
Change-Id: Ia3405e7dc18cb11026927836d07be5e3271817bb
Reviewed-on: https://chromium-review.googlesource.com/921227
Commit-Queue: Morten Stenshorne <mstensho@chromium.org>
Reviewed-by: Koji Ishii <kojii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#537005}

third_party/WebKit/Source/core/layout/LayoutMultiColumnFlowThread.cpp

@@ -687,6 +687,17 @@ void LayoutMultiColumnFlowThread::AppendNewFragmentainerGroupIfNeeded(
   }
 }
 
+void LayoutMultiColumnFlowThread::UpdateFromNG() {
+  all_columns_have_known_height_ = true;
+  for (LayoutBox* column_box = FirstMultiColumnBox(); column_box;
+       column_box = column_box->NextSiblingMultiColumnBox()) {
+    if (column_box->IsLayoutMultiColumnSet())
+      ToLayoutMultiColumnSet(column_box)->UpdateFromNG();
+    column_box->ClearNeedsLayout();
+    column_box->UpdateAfterLayout();
+  }
+}
+
 bool LayoutMultiColumnFlowThread::IsFragmentainerLogicalHeightKnown() {
   return IsPageLogicalHeightKnown();
 }

third_party/WebKit/Source/core/layout/LayoutMultiColumnFlowThread.h

@@ -281,6 +281,8 @@ class CORE_EXPORT LayoutMultiColumnFlowThread : public LayoutFlowThread,
   void AppendNewFragmentainerGroupIfNeeded(LayoutUnit offset_in_flow_thread,
                                            PageBoundaryRule);
 
+  void UpdateFromNG();
+
   // Implementing FragmentationContext:
   bool IsFragmentainerLogicalHeightKnown() final;
   LayoutUnit FragmentainerLogicalHeightAt(LayoutUnit block_offset) final;

third_party/WebKit/Source/core/layout/LayoutMultiColumnSet.cpp

@@ -653,7 +653,6 @@ void LayoutMultiColumnSet::UpdateFromNG() {
   auto& group = fragmentainer_groups_[0];
   group.UpdateFromNG(LogicalHeight());
   ComputeOverflow(LogicalHeight());
-  ClearNeedsLayout();
 }
 
 }  // namespace blink

third_party/WebKit/Source/core/layout/ng/ng_block_node.cc

@@ -104,16 +104,11 @@ void UpdateLegacyMultiColumnFlowThread(
                                 border_scrollbar_padding.InlineSum());
     column_set->SetLogicalHeight(column_block_size);
     column_set->EndFlow(flow_end);
-    column_set->UpdateFromNG();
   }
   // TODO(mstensho): Update all column boxes, not just the first column set
   // (like we do above). This is needed to support column-span:all.
-  for (LayoutBox* column_box = flow_thread->FirstMultiColumnBox(); column_box;
-       column_box = column_box->NextSiblingMultiColumnBox()) {
-    column_box->ClearNeedsLayout();
-    column_box->UpdateAfterLayout();
-  }
 
+  flow_thread->UpdateFromNG();
   flow_thread->ValidateColumnSets();
   flow_thread->SetLogicalHeight(flow_end);
   flow_thread->UpdateAfterLayout();