[mathml] Implement the <munder>, <mover>, <munderover> elements

Implement the <munder>, <mover>, <munderover> elements and add a layout
algorithm [1] covering all three elements. This patch does
not yet cover all details of the algorithm (accent, stretchy operators)
to keep the patch simple, however FIXMEs are added.

[1] https://mathml-refresh.github.io/mathml-core/#underscripts-and-overscripts-munder-mover-munderover

Bug: 6606
Change-Id: I8a20bb3105b733ef57413114aed0e6b536597c46
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2119538
Commit-Queue: Rob Buis <rbuis@igalia.com>
Reviewed-by: Ian Kilpatrick <ikilpatrick@chromium.org>
Reviewed-by: Morten Stenshorne <mstensho@chromium.org>
Reviewed-by: Mason Freed <masonfreed@chromium.org>
Cr-Commit-Position: refs/heads/master@{#756225}

third_party/blink/renderer/core/css/mathml.css

@@ -46,7 +46,7 @@ math[display="block"] {
     outline: auto 1px -webkit-focus-ring-color;
 }
 
-maction, merror, mfrac, mphantom, mrow, mspace, mstyle
+maction, merror, mfrac, mphantom, mrow, mspace, mstyle, munder, mover, munderover
 {
     display: math;
 }

third_party/blink/renderer/core/layout/BUILD.gn

@@ -427,6 +427,8 @@ blink_core_sources("layout") {
     "ng/mathml/ng_math_row_layout_algorithm.h",
     "ng/mathml/ng_math_space_layout_algorithm.cc",
     "ng/mathml/ng_math_space_layout_algorithm.h",
+    "ng/mathml/ng_math_under_over_layout_algorithm.cc",
+    "ng/mathml/ng_math_under_over_layout_algorithm.h",
     "ng/ng_absolute_utils.cc",
     "ng/ng_absolute_utils.h",
     "ng/ng_block_break_token.cc",

third_party/blink/renderer/core/layout/ng/mathml/ng_math_layout_utils.cc

@@ -10,6 +10,7 @@
 #include "third_party/blink/renderer/core/layout/ng/ng_length_utils.h"
 #include "third_party/blink/renderer/core/layout/ng/ng_space_utils.h"
 #include "third_party/blink/renderer/core/mathml/mathml_fraction_element.h"
+#include "third_party/blink/renderer/core/mathml/mathml_under_over_element.h"
 
 namespace blink {
 
@@ -69,6 +70,21 @@ bool IsValidMathMLFraction(const NGBlockNode& node) {
   return InFlowChildCountIs(node, 2);
 }
 
+bool IsValidMathMLUnderOver(const NGBlockNode& node) {
+  auto* scripted =
+      DynamicTo<MathMLUnderOverElement>(node.GetLayoutBox()->GetNode());
+  switch (scripted->scriptType()) {
+    case MathMLUnderOverElement::ScriptType::kUnder:
+    case MathMLUnderOverElement::ScriptType::kOver:
+      return InFlowChildCountIs(node, 2);
+    case MathMLUnderOverElement::ScriptType::kUnderOver:
+      return InFlowChildCountIs(node, 3);
+    default:
+      NOTREACHED();
+      return false;
+  }
+}
+
 namespace {
 
 inline LayoutUnit DefaultFractionLineThickness(const ComputedStyle& style) {

third_party/blink/renderer/core/layout/ng/mathml/ng_math_layout_utils.h

@@ -26,6 +26,7 @@ NGLayoutInputNode FirstChildInFlow(const NGBlockNode&);
 NGLayoutInputNode NextSiblingInFlow(const NGBlockNode&);
 
 bool IsValidMathMLFraction(const NGBlockNode&);
+bool IsValidMathMLUnderOver(const NGBlockNode&);
 
 inline float RuleThicknessFallback(const ComputedStyle& style) {
   // This function returns a value for the default rule thickness (TeX's

third_party/blink/renderer/core/layout/ng/mathml/ng_math_under_over_layout_algorithm.h

+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef THIRD_PARTY_BLINK_RENDERER_CORE_LAYOUT_NG_MATHML_NG_MATH_UNDER_OVER_LAYOUT_ALGORITHM_H_
+#define THIRD_PARTY_BLINK_RENDERER_CORE_LAYOUT_NG_MATHML_NG_MATH_UNDER_OVER_LAYOUT_ALGORITHM_H_
+
+#include "third_party/blink/renderer/core/layout/ng/ng_box_fragment_builder.h"
+#include "third_party/blink/renderer/core/layout/ng/ng_layout_algorithm.h"
+
+namespace blink {
+
+class CORE_EXPORT NGMathUnderOverLayoutAlgorithm
+    : public NGLayoutAlgorithm<NGBlockNode,
+                               NGBoxFragmentBuilder,
+                               NGBlockBreakToken> {
+ public:
+  explicit NGMathUnderOverLayoutAlgorithm(
+      const NGLayoutAlgorithmParams& params);
+
+  scoped_refptr<const NGLayoutResult> Layout() override;
+
+  base::Optional<MinMaxSizes> ComputeMinMaxSizes(
+      const MinMaxSizesInput&) const override;
+
+ private:
+  void GatherChildren(NGBlockNode* base,
+                      NGBlockNode* second,
+                      NGBlockNode* third);
+
+  const NGBoxStrut border_scrollbar_padding_;
+};
+
+}  // namespace blink
+
+#endif  // THIRD_PARTY_BLINK_RENDERER_CORE_LAYOUT_NG_MATHML_NG_MATH_UNDER_OVER_LAYOUT_ALGORITHM_H_

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

@@ -33,6 +33,7 @@
 #include "third_party/blink/renderer/core/layout/ng/mathml/ng_math_layout_utils.h"
 #include "third_party/blink/renderer/core/layout/ng/mathml/ng_math_row_layout_algorithm.h"
 #include "third_party/blink/renderer/core/layout/ng/mathml/ng_math_space_layout_algorithm.h"
+#include "third_party/blink/renderer/core/layout/ng/mathml/ng_math_under_over_layout_algorithm.h"
 #include "third_party/blink/renderer/core/layout/ng/ng_block_break_token.h"
 #include "third_party/blink/renderer/core/layout/ng/ng_block_layout_algorithm.h"
 #include "third_party/blink/renderer/core/layout/ng/ng_box_fragment.h"
@@ -55,6 +56,7 @@
 #include "third_party/blink/renderer/core/mathml/mathml_element.h"
 #include "third_party/blink/renderer/core/mathml/mathml_fraction_element.h"
 #include "third_party/blink/renderer/core/mathml/mathml_space_element.h"
+#include "third_party/blink/renderer/core/mathml/mathml_under_over_element.h"
 #include "third_party/blink/renderer/core/paint/paint_layer_scrollable_area.h"
 #include "third_party/blink/renderer/platform/runtime_enabled_features.h"
 #include "third_party/blink/renderer/platform/text/writing_mode.h"
@@ -104,6 +106,9 @@ NOINLINE void DetermineMathMLAlgorithmAndRun(
   else if (IsA<MathMLFractionElement>(element) &&
            IsValidMathMLFraction(params.node))
     CreateAlgorithmAndRun<NGMathFractionLayoutAlgorithm>(params, callback);
+  else if (IsA<MathMLUnderOverElement>(element) &&
+           IsValidMathMLUnderOver(params.node))
+    CreateAlgorithmAndRun<NGMathUnderOverLayoutAlgorithm>(params, callback);
   else
     CreateAlgorithmAndRun<NGMathRowLayoutAlgorithm>(params, callback);
 }

third_party/blink/renderer/core/mathml/BUILD.gn

@@ -14,5 +14,7 @@ blink_core_sources("mathml") {
     "mathml_row_element.h",
     "mathml_space_element.cc",
     "mathml_space_element.h",
+    "mathml_under_over_element.cc",
+    "mathml_under_over_element.h",
   ]
 }

third_party/blink/renderer/core/mathml/mathml_tag_names.json5

@@ -75,6 +75,18 @@
       name: "mtext",
       interfaceName: "MathMLElement",
     },
+    {
+      name: "mover",
+      interfaceName: "MathMLUnderOverElement",
+    },
+    {
+      name: "munder",
+      interfaceName: "MathMLUnderOverElement",
+    },
+    {
+      name: "munderover",
+      interfaceName: "MathMLUnderOverElement",
+    },
     {
       name: "semantics",
       interfaceName: "MathMLRowElement",

third_party/blink/renderer/core/mathml/mathml_under_over_element.cc

+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "third_party/blink/renderer/core/mathml/mathml_under_over_element.h"
+
+#include "third_party/blink/renderer/core/layout/ng/mathml/layout_ng_mathml_block.h"
+#include "third_party/blink/renderer/platform/runtime_enabled_features.h"
+
+namespace blink {
+
+static MathMLUnderOverElement::ScriptType scriptTypeOf(
+    const QualifiedName& tagName) {
+  if (tagName == mathml_names::kMunderTag)
+    return MathMLUnderOverElement::ScriptType::kUnder;
+  if (tagName == mathml_names::kMoverTag)
+    return MathMLUnderOverElement::ScriptType::kOver;
+  DCHECK_EQ(tagName, mathml_names::kMunderoverTag);
+  return MathMLUnderOverElement::ScriptType::kUnderOver;
+}
+
+MathMLUnderOverElement::MathMLUnderOverElement(const QualifiedName& tagName,
+                                               Document& document)
+    : MathMLElement(tagName, document), script_type_(scriptTypeOf(tagName)) {}
+
+LayoutObject* MathMLUnderOverElement::CreateLayoutObject(
+    const ComputedStyle& style,
+    LegacyLayout legacy) {
+  if (!RuntimeEnabledFeatures::MathMLCoreEnabled() ||
+      !style.IsDisplayMathType() || legacy == LegacyLayout::kForce)
+    return MathMLElement::CreateLayoutObject(style, legacy);
+  return new LayoutNGMathMLBlock(this);
+}
+
+}  // namespace blink

third_party/blink/renderer/core/mathml/mathml_under_over_element.h

+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef THIRD_PARTY_BLINK_RENDERER_CORE_MATHML_MATHML_UNDER_OVER_ELEMENT_H_
+#define THIRD_PARTY_BLINK_RENDERER_CORE_MATHML_MATHML_UNDER_OVER_ELEMENT_H_
+
+#include "third_party/blink/renderer/core/mathml/mathml_element.h"
+
+namespace blink {
+
+class Document;
+
+class CORE_EXPORT MathMLUnderOverElement final : public MathMLElement {
+ public:
+  MathMLUnderOverElement(const QualifiedName& tagName, Document& document);
+
+  enum class ScriptType {
+    kUnder,
+    kOver,
+    kUnderOver,
+  };
+  ScriptType scriptType() const { return script_type_; }
+
+ private:
+  const ScriptType script_type_;
+  LayoutObject* CreateLayoutObject(const ComputedStyle&,
+                                   LegacyLayout legacy) override;
+};
+
+template <>
+inline bool IsElementOfType<const MathMLUnderOverElement>(const Node& node) {
+  return IsA<MathMLUnderOverElement>(node);
+}
+template <>
+struct DowncastTraits<MathMLUnderOverElement> {
+  static bool AllowFrom(const Node& node) {
+    auto* mathml_element = DynamicTo<MathMLElement>(node);
+    return mathml_element && AllowFrom(*mathml_element);
+  }
+  static bool AllowFrom(const MathMLElement& mathml_element) {
+    return mathml_element.HasTagName(mathml_names::kMunderTag) ||
+           mathml_element.HasTagName(mathml_names::kMoverTag) ||
+           mathml_element.HasTagName(mathml_names::kMunderoverTag);
+  }
+};
+
+}  // namespace blink
+
+#endif  // THIRD_PARTY_BLINK_RENDERER_CORE_MATHML_MATHML_UNDER_OVER_ELEMENT_H_

third_party/blink/web_tests/TestExpectations

@@ -1630,6 +1630,7 @@ crbug.com/6606 external/wpt/mathml/presentation-markup/operators/mo-axis-height-
 crbug.com/6606 external/wpt/mathml/presentation-markup/operators/mo-form-dynamic.html [ Failure ]
 crbug.com/6606 external/wpt/mathml/presentation-markup/operators/mo-form-minus-plus.html [ Failure ]
 crbug.com/6606 external/wpt/mathml/presentation-markup/operators/mo-form.html [ Failure ]
+crbug.com/6606 external/wpt/mathml/presentation-markup/operators/mo-movablelimits.html [ Failure ]
 crbug.com/6606 external/wpt/mathml/presentation-markup/operators/mo-paint-lspace-rspace.html [ Failure ]
 crbug.com/6606 external/wpt/mathml/presentation-markup/operators/operator-dictionary-001.html [ Failure ]
 crbug.com/6606 external/wpt/mathml/presentation-markup/operators/operator-dictionary-002.html [ Failure ]
@@ -1640,8 +1641,6 @@ crbug.com/6606 external/wpt/mathml/presentation-markup/scripts/subsup-3.html [ F
 crbug.com/6606 external/wpt/mathml/presentation-markup/scripts/subsup-5.html [ Failure ]
 crbug.com/6606 external/wpt/mathml/presentation-markup/scripts/subsup-parameters-1.html [ Failure ]
 crbug.com/6606 external/wpt/mathml/presentation-markup/scripts/subsup-parameters-2.html [ Failure ]
-crbug.com/6606 external/wpt/mathml/presentation-markup/scripts/underover-1.html [ Failure ]
-crbug.com/6606 external/wpt/mathml/presentation-markup/scripts/underover-parameters-1.html [ Failure ]
 crbug.com/6606 external/wpt/mathml/presentation-markup/scripts/underover-parameters-2.html [ Failure ]
 crbug.com/6606 external/wpt/mathml/presentation-markup/scripts/underover-parameters-3.html [ Failure ]
 crbug.com/6606 external/wpt/mathml/presentation-markup/scripts/underover-parameters-4.html [ Failure ]
@@ -1680,9 +1679,6 @@ crbug.com/6606 external/wpt/mathml/relations/css-styling/mathvariant-sans-serif.
 crbug.com/6606 external/wpt/mathml/relations/css-styling/mathvariant-script.html [ Failure ]
 crbug.com/6606 external/wpt/mathml/relations/css-styling/mathvariant-stretched.html [ Failure ]
 crbug.com/6606 external/wpt/mathml/relations/css-styling/mathvariant-tailed.html [ Failure ]
-crbug.com/6606 external/wpt/mathml/relations/css-styling/padding-border-margin/border-002.html [ Failure ]
-crbug.com/6606 external/wpt/mathml/relations/css-styling/padding-border-margin/margin-002.html [ Failure ]
-crbug.com/6606 external/wpt/mathml/relations/css-styling/padding-border-margin/padding-002.html [ Failure ]
 crbug.com/6606 external/wpt/mathml/relations/css-styling/visibility-003.html [ Failure ]
 crbug.com/6606 external/wpt/mathml/relations/css-styling/width-height-001.html [ Failure ]
 crbug.com/6606 external/wpt/mathml/relations/html5-tree/href-click-1.html [ Failure ]

third_party/blink/web_tests/external/wpt/mathml/relations/css-styling/padding-border-margin/border-002-expected.txt

+This is a testharness.js-based test.
+PASS Border properties on maction
+PASS Border properties on maction (rtl)
+PASS Border properties on menclose
+PASS Border properties on menclose (rtl)
+PASS Border properties on merror
+PASS Border properties on merror (rtl)
+PASS Border properties on mfrac
+PASS Border properties on mfrac (rtl)
+PASS Border properties on mi
+PASS Border properties on mi (rtl)
+PASS Border properties on mmultiscripts
+PASS Border properties on mmultiscripts (rtl)
+PASS Border properties on mn
+PASS Border properties on mn (rtl)
+PASS Border properties on mo
+PASS Border properties on mo (rtl)
+PASS Border properties on mover
+PASS Border properties on mover (rtl)
+PASS Border properties on mpadded
+PASS Border properties on mpadded (rtl)
+PASS Border properties on mphantom
+PASS Border properties on mphantom (rtl)
+FAIL Border properties on mroot assert_true: mroot is supported expected true got false
+FAIL Border properties on mroot (rtl) assert_true: mroot is supported expected true got false
+PASS Border properties on mrow
+PASS Border properties on mrow (rtl)
+PASS Border properties on ms
+PASS Border properties on ms (rtl)
+PASS Border properties on mspace
+FAIL Border properties on msqrt assert_true: msqrt is supported expected true got false
+FAIL Border properties on msqrt (rtl) assert_true: msqrt is supported expected true got false
+PASS Border properties on mstyle
+PASS Border properties on mstyle (rtl)
+PASS Border properties on msub
+PASS Border properties on msub (rtl)
+PASS Border properties on msubsup
+PASS Border properties on msubsup (rtl)
+PASS Border properties on msup
+PASS Border properties on msup (rtl)
+PASS Border properties on mtable
+PASS Border properties on mtable (rtl)
+PASS Border properties on mtext
+PASS Border properties on mtext (rtl)
+PASS Border properties on munder
+PASS Border properties on munder (rtl)
+PASS Border properties on munderover
+PASS Border properties on munderover (rtl)
+PASS Border properties on semantics
+PASS Border properties on semantics (rtl)
+Harness: the test ran to completion.
+

third_party/blink/web_tests/external/wpt/mathml/relations/css-styling/padding-border-margin/margin-002-expected.txt

+This is a testharness.js-based test.
+Found 73 tests; 67 PASS, 6 FAIL, 0 TIMEOUT, 0 NOTRUN.
+PASS Margin properties on maction
+PASS Margin properties on maction (rtl)
+PASS Margin properties on maction (no margin-collapsing)
+PASS Margin properties on menclose
+PASS Margin properties on menclose (rtl)
+PASS Margin properties on menclose (no margin-collapsing)
+PASS Margin properties on merror
+PASS Margin properties on merror (rtl)
+PASS Margin properties on merror (no margin-collapsing)
+PASS Margin properties on mfrac
+PASS Margin properties on mfrac (rtl)
+PASS Margin properties on mfrac (no margin-collapsing)
+PASS Margin properties on mi
+PASS Margin properties on mi (rtl)
+PASS Margin properties on mi (no margin-collapsing)
+PASS Margin properties on mmultiscripts
+PASS Margin properties on mmultiscripts (rtl)
+PASS Margin properties on mmultiscripts (no margin-collapsing)
+PASS Margin properties on mn
+PASS Margin properties on mn (rtl)
+PASS Margin properties on mn (no margin-collapsing)
+PASS Margin properties on mo
+PASS Margin properties on mo (rtl)
+PASS Margin properties on mo (no margin-collapsing)
+PASS Margin properties on mover
+PASS Margin properties on mover (rtl)
+PASS Margin properties on mover (no margin-collapsing)
+PASS Margin properties on mpadded
+PASS Margin properties on mpadded (rtl)
+PASS Margin properties on mpadded (no margin-collapsing)
+PASS Margin properties on mphantom
+PASS Margin properties on mphantom (rtl)
+PASS Margin properties on mphantom (no margin-collapsing)
+FAIL Margin properties on mroot assert_true: mroot is supported expected true got false
+FAIL Margin properties on mroot (rtl) assert_true: mroot is supported expected true got false
+FAIL Margin properties on mroot (no margin-collapsing) assert_true: mroot is supported expected true got false
+PASS Margin properties on mrow
+PASS Margin properties on mrow (rtl)
+PASS Margin properties on mrow (no margin-collapsing)
+PASS Margin properties on ms
+PASS Margin properties on ms (rtl)
+PASS Margin properties on ms (no margin-collapsing)
+PASS Margin properties on mspace
+FAIL Margin properties on msqrt assert_true: msqrt is supported expected true got false
+FAIL Margin properties on msqrt (rtl) assert_true: msqrt is supported expected true got false
+FAIL Margin properties on msqrt (no margin-collapsing) assert_true: msqrt is supported expected true got false
+PASS Margin properties on mstyle
+PASS Margin properties on mstyle (rtl)
+PASS Margin properties on mstyle (no margin-collapsing)
+PASS Margin properties on msub
+PASS Margin properties on msub (rtl)
+PASS Margin properties on msub (no margin-collapsing)
+PASS Margin properties on msubsup
+PASS Margin properties on msubsup (rtl)
+PASS Margin properties on msubsup (no margin-collapsing)
+PASS Margin properties on msup
+PASS Margin properties on msup (rtl)
+PASS Margin properties on msup (no margin-collapsing)
+PASS Margin properties on mtable
+PASS Margin properties on mtable (rtl)
+PASS Margin properties on mtable (no margin-collapsing)
+PASS Margin properties on mtext
+PASS Margin properties on mtext (rtl)
+PASS Margin properties on mtext (no margin-collapsing)
+PASS Margin properties on munder
+PASS Margin properties on munder (rtl)
+PASS Margin properties on munder (no margin-collapsing)
+PASS Margin properties on munderover
+PASS Margin properties on munderover (rtl)
+PASS Margin properties on munderover (no margin-collapsing)
+PASS Margin properties on semantics
+PASS Margin properties on semantics (rtl)
+PASS Margin properties on semantics (no margin-collapsing)
+Harness: the test ran to completion.
+

third_party/blink/web_tests/external/wpt/mathml/relations/css-styling/padding-border-margin/margin-003-expected.txt

+This is a testharness.js-based test.
+PASS Margin properties on the children of menclose
+PASS Margin properties on the children of merror
+PASS Margin properties on the children of mfrac
+FAIL Margin properties on the children of mmultiscripts assert_approx_equals: block size expected 345 +/- 1 but got 305
+PASS Margin properties on the children of mover
+PASS Margin properties on the children of mpadded
+PASS Margin properties on the children of mphantom
+FAIL Margin properties on the children of mroot assert_true: mroot is supported expected true got false
+PASS Margin properties on the children of mrow
+FAIL Margin properties on the children of msqrt assert_true: msqrt is supported expected true got false
+PASS Margin properties on the children of mstyle
+FAIL Margin properties on the children of msub assert_approx_equals: block size expected 230 +/- 1 but got 210
+FAIL Margin properties on the children of msubsup assert_approx_equals: block size expected 345 +/- 1 but got 305
+FAIL Margin properties on the children of msup assert_approx_equals: block size expected 230 +/- 1 but got 210
+PASS Margin properties on the children of munder
+PASS Margin properties on the children of munderover
+Harness: the test ran to completion.
+

third_party/blink/web_tests/external/wpt/mathml/relations/css-styling/padding-border-margin/margin-003.html

+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8">
+<title>margin</title>
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#layout-algorithms">
+<meta name="assert" content="Verify that margin is taken into account on children.">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/mathml/support/feature-detection.js"></script>
+<script src="/mathml/support/mathml-fragments.js"></script>
+<script src="/mathml/support/layout-comparison.js"></script>
+<script>
+  var epsilon = 1;
+
+  setup({ explicit_done: true });
+  window.addEventListener("load", runTests);
+
+  function runTests() {
+
+    for (tag in MathMLFragments) {
+        if (!FragmentHelper.isValidChildOfMrow(tag) ||
+            FragmentHelper.isEmpty(tag) ||
+            FragmentHelper.isTokenElement(tag) ||
+            tag == "semantics" ||
+            tag == "maction" ||
+            tag == "mtable")
+            continue;
+
+        test(function() {
+            assert_true(MathMLFeatureDetection[`has_${tag}`](), `${tag} is supported`);
+
+            document.body.insertAdjacentHTML("beforeend", `<hr/><div>\
+<div style="display: inline-block; border: 1px dashed blue;"><math>${MathMLFragments[tag]}</math></div><br/>\
+<div style="display: inline-block; border: 1px dashed green;"><math>${MathMLFragments[tag]}</math></div>\
+</div>`);
+
+            var div = document.body.lastElementChild;
+            var elementShrinkWrapContainer = div.firstElementChild;
+            var element = elementShrinkWrapContainer.firstElementChild.firstElementChild;
+            var elementContainer = div.firstElementChild;
+            var referenceShrinkWrapContainer = div.lastElementChild;
+            var reference = referenceShrinkWrapContainer.firstElementChild.firstElementChild;
+
+            FragmentHelper.forceNonEmptyElement(element);
+            FragmentHelper.forceNonEmptyElement(reference);
+
+            var mspaceWidth = 20, mspaceHeight = 40, mspaceDepth = 30;
+            var marginLeft = 10, marginRight = 15, marginTop = 20, marginBottom = 25;
+            Array.from(element.children).forEach(mrow => {
+                mrow.outerHTML = `<mspace width="${mspaceWidth}px" height="${mspaceHeight}px" depth='${mspaceDepth}px' style='background: blue; margin-left: ${marginLeft}px; margin-right: ${marginRight}px;  margin-top: ${marginTop}px; margin-bottom: ${marginBottom}px;'></mspace>`;
+            });
+
+            Array.from(reference.children).forEach(mrow => {
+                mrow.outerHTML = `<mspace width="${marginLeft+mspaceWidth+marginRight}px" height="${mspaceHeight+marginTop}px" depth='${mspaceDepth+marginBottom}px' style='background: green;'></mspace>`;
+            });
+
+            // Compare sizes.
+            compareSize(element, reference, epsilon);
+
+            // Compare children positions.
+            var elementBox = element.getBoundingClientRect();
+            var referenceBox = reference.getBoundingClientRect();
+            for (var i = 0; i < element.children.length; i++) {
+                var childBox = element.children[i].getBoundingClientRect();
+                var referenceChildBox = reference.children[i].getBoundingClientRect();
+                assert_approx_equals(childBox.width + marginLeft + marginRight, referenceChildBox.width, epsilon, "inline size (child ${i})");
+                assert_approx_equals(childBox.height + marginTop + marginBottom, referenceChildBox.height, epsilon, "block size (child ${i})");
+
+                assert_approx_equals(childBox.left - marginLeft - elementBox.left,
+                                     referenceChildBox.left - referenceBox.left,
+                                     epsilon,
+                                     `inline position (child ${i})`);
+                assert_approx_equals(childBox.top - marginTop - elementBox.top,
+                                     referenceChildBox.top - referenceBox.top,
+                                     epsilon,
+                                     `block position (child ${i})`);
+            }
+
+            // Compare preferred widths.
+            assert_approx_equals(elementShrinkWrapContainer.offsetWidth, referenceShrinkWrapContainer.offsetWidth, epsilon, "preferred width");
+
+        }, `Margin properties on the children of ${tag}`);
+    }
+
+    done();
+  }
+</script>
+</head>
+<body>
+  <div id="log"></div>
+</body>
+</html>

third_party/blink/web_tests/external/wpt/mathml/relations/css-styling/padding-border-margin/padding-002-expected.txt

+This is a testharness.js-based test.
+PASS Padding properties on maction
+PASS Padding properties on maction (rtl)
+PASS Padding properties on menclose
+PASS Padding properties on menclose (rtl)
+PASS Padding properties on merror
+PASS Padding properties on merror (rtl)
+PASS Padding properties on mfrac
+PASS Padding properties on mfrac (rtl)
+PASS Padding properties on mi
+PASS Padding properties on mi (rtl)
+PASS Padding properties on mmultiscripts
+PASS Padding properties on mmultiscripts (rtl)
+PASS Padding properties on mn
+PASS Padding properties on mn (rtl)
+PASS Padding properties on mo
+PASS Padding properties on mo (rtl)
+PASS Padding properties on mover
+PASS Padding properties on mover (rtl)
+PASS Padding properties on mpadded
+PASS Padding properties on mpadded (rtl)
+PASS Padding properties on mphantom
+PASS Padding properties on mphantom (rtl)
+FAIL Padding properties on mroot assert_true: mroot is supported expected true got false
+FAIL Padding properties on mroot (rtl) assert_true: mroot is supported expected true got false
+PASS Padding properties on mrow
+PASS Padding properties on mrow (rtl)
+PASS Padding properties on ms
+PASS Padding properties on ms (rtl)
+PASS Padding properties on mspace
+FAIL Padding properties on msqrt assert_true: msqrt is supported expected true got false
+FAIL Padding properties on msqrt (rtl) assert_true: msqrt is supported expected true got false
+PASS Padding properties on mstyle
+PASS Padding properties on mstyle (rtl)
+PASS Padding properties on msub
+PASS Padding properties on msub (rtl)
+PASS Padding properties on msubsup
+PASS Padding properties on msubsup (rtl)
+PASS Padding properties on msup
+PASS Padding properties on msup (rtl)
+PASS Padding properties on mtable
+PASS Padding properties on mtable (rtl)
+PASS Padding properties on mtext
+PASS Padding properties on mtext (rtl)
+PASS Padding properties on munder
+PASS Padding properties on munder (rtl)
+PASS Padding properties on munderover
+PASS Padding properties on munderover (rtl)
+PASS Padding properties on semantics
+PASS Padding properties on semantics (rtl)
+Harness: the test ran to completion.
+

third_party/blink/web_tests/external/wpt/mathml/support/mathml-fragments.js

@@ -132,6 +132,14 @@ var FragmentHelper = {
                  tag == "mtd");
     },
 
+    isTokenElement: function(tag) {
+        return (tag == "mi" ||
+                tag == "mtext" ||
+                tag == "mo" ||
+                tag == "mn" ||
+                tag == "ms")
+    },
+
     isEmpty: function(tag) {
         return tag === "mspace" || tag == "mprescripts" || tag == "none";
     },