Copy 'name_' member during StyleRuleProperty::Copy

This was neglected, end therefore ends up as a null-string in the copy,
causing crashes.

Bug: 1134550
Change-Id: Ib2d5cf649e10d2d510417a43edd3189617092514
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2445470Reviewed-by: Rune Lillesveen <futhark@chromium.org>
Commit-Queue: Anders Hartvoll Ruud <andruud@chromium.org>
Cr-Commit-Position: refs/heads/master@{#813218}

third_party/blink/renderer/core/css/style_rule.cc

@@ -332,6 +332,7 @@ StyleRuleProperty::StyleRuleProperty(const String& name,
 
 StyleRuleProperty::StyleRuleProperty(const StyleRuleProperty& property_rule)
     : StyleRuleBase(property_rule),
+      name_(property_rule.name_),
       properties_(property_rule.properties_->MutableCopy()) {}
 
 StyleRuleProperty::~StyleRuleProperty() = default;

third_party/blink/renderer/core/css/style_rule.h

@@ -188,7 +188,7 @@ class StyleRulePage : public StyleRuleBase {
   CSSSelectorList selector_list_;
 };
 
-class StyleRuleProperty : public StyleRuleBase {
+class CORE_EXPORT StyleRuleProperty : public StyleRuleBase {
  public:
   StyleRuleProperty(const String& name, CSSPropertyValueSet*);
   StyleRuleProperty(const StyleRuleProperty&);

third_party/blink/renderer/core/css/style_rule_test.cc

@@ -77,4 +77,33 @@ TEST_F(StyleRuleTest, StyleRuleScrollTimelineCopy) {
   EXPECT_EQ(rule->GetTimeRange(), copy->GetTimeRange());
 }
 
+TEST_F(StyleRuleTest, StyleRulePropertyCopy) {
+  ScopedCSSVariables2AtPropertyForTest scoped_feature(true);
+
+  auto* base_rule = css_test_helpers::ParseRule(GetDocument(), R"CSS(
+      @property --foo {
+        syntax: "<length>";
+        initial-value: 0px;
+        inherits: false;
+      }
+    )CSS");
+
+  ASSERT_TRUE(base_rule);
+  auto* base_copy = base_rule->Copy();
+
+  EXPECT_NE(base_rule, base_copy);
+  EXPECT_EQ(base_rule->GetType(), base_copy->GetType());
+
+  auto* rule = DynamicTo<StyleRuleProperty>(base_rule);
+  auto* copy = DynamicTo<StyleRuleProperty>(base_copy);
+
+  ASSERT_TRUE(rule);
+  ASSERT_TRUE(copy);
+
+  EXPECT_EQ(rule->GetName(), copy->GetName());
+  EXPECT_EQ(rule->GetSyntax(), copy->GetSyntax());
+  EXPECT_EQ(rule->Inherits(), copy->Inherits());
+  EXPECT_EQ(rule->GetInitialValue(), copy->GetInitialValue());
+}
+
 }  // namespace blink