Opt out of anonymous style propagation for spanner placeholders.

LayoutObject::PropagateStyleToAnonymousChildren() doesn't do the right
thing for LayoutMultiColumnSpannerPlaceholder. Spanner placeholders need
to copy the margins from the actual spanner object, in addition to
inheriting properties from the parent of the actual spanner.

Bug: 903699
Change-Id: I4252c546610eca2698efd523f98f20a98627d217
Reviewed-on: https://chromium-review.googlesource.com/c/1328986
Commit-Queue: Morten Stenshorne <mstensho@chromium.org>
Reviewed-by: Rune Lillesveen <futhark@chromium.org>
Cr-Commit-Position: refs/heads/master@{#607179}

third_party/WebKit/LayoutTests/TestExpectations

@@ -2889,7 +2889,6 @@ crbug.com/893480 external/wpt/infrastructure/testdriver/actions/multiDevice.html
 # ====== New tests from wpt-importer added here ======
 crbug.com/626703 virtual/layout_ng_experimental/external/wpt/css/css-multicol/multicol-margin-003.html [ Failure ]
 crbug.com/626703 external/wpt/css/css-multicol/multicol-margin-003.html [ Failure ]
-crbug.com/626703 external/wpt/css/css-multicol/multicol-span-all-restyle-003.html [ Failure ]
 crbug.com/626703 external/wpt/css/filter-effects/filter-grayscale-003.html [ Failure ]
 crbug.com/626703 external/wpt/css/filter-effects/filter-grayscale-002.html [ Failure ]
 crbug.com/626703 external/wpt/css/filter-effects/filter-external-002-test.html [ Failure ]

third_party/blink/renderer/core/layout/layout_multi_column_spanner_placeholder.cc

@@ -27,11 +27,7 @@ LayoutMultiColumnSpannerPlaceholder::CreateAnonymous(
       new LayoutMultiColumnSpannerPlaceholder(&layout_object_in_flow_thread);
   Document& document = layout_object_in_flow_thread.GetDocument();
   new_spanner->SetDocumentForAnonymous(&document);
-  scoped_refptr<ComputedStyle> new_style =
-      ComputedStyle::CreateAnonymousStyleWithDisplay(parent_style,
-                                                     EDisplay::kBlock);
-  CopyMarginProperties(*new_style, layout_object_in_flow_thread.StyleRef());
-  new_spanner->SetStyle(new_style);
+  new_spanner->UpdateProperties(parent_style);
   return new_spanner;
 }
 
@@ -60,13 +56,16 @@ void LayoutMultiColumnSpannerPlaceholder::
     }
     return;
   }
-  UpdateMarginProperties();
+  UpdateProperties(Parent()->StyleRef());
 }
 
-void LayoutMultiColumnSpannerPlaceholder::UpdateMarginProperties() {
-  scoped_refptr<ComputedStyle> new_style = ComputedStyle::Clone(StyleRef());
+void LayoutMultiColumnSpannerPlaceholder::UpdateProperties(
+    const ComputedStyle& parent_style) {
+  scoped_refptr<ComputedStyle> new_style =
+      ComputedStyle::CreateAnonymousStyleWithDisplay(parent_style,
+                                                     EDisplay::kBlock);
   CopyMarginProperties(*new_style, layout_object_in_flow_thread_->StyleRef());
-  SetStyle(new_style);
+  SetStyle(std::move(new_style));
 }
 
 void LayoutMultiColumnSpannerPlaceholder::InsertedIntoTree() {

third_party/blink/renderer/core/layout/layout_multi_column_spanner_placeholder.h

@@ -42,8 +42,10 @@ class LayoutMultiColumnSpannerPlaceholder final : public LayoutBox {
     SetChildNeedsLayout(kMarkOnlyThis);
   }
 
+  bool AnonymousHasStylePropagationOverride() final { return true; }
+
   void LayoutObjectInFlowThreadStyleDidChange(const ComputedStyle* old_style);
-  void UpdateMarginProperties();
+  void UpdateProperties(const ComputedStyle& parent_style);
 
   const char* GetName() const override {
     return "LayoutMultiColumnSpannerPlaceholder";