--- a/layout/inspector/ServoStyleRuleMap.cpp
+++ b/layout/inspector/ServoStyleRuleMap.cpp
@@ -2,21 +2,21 @@
 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #include "mozilla/ServoStyleRuleMap.h"
 
 #include "mozilla/css/GroupRule.h"
+#include "mozilla/dom/CSSImportRule.h"
 #include "mozilla/dom/CSSRuleBinding.h"
 #include "mozilla/dom/CSSStyleRule.h"
 #include "mozilla/IntegerRange.h"
 #include "mozilla/ServoStyleSet.h"
-#include "mozilla/ServoImportRule.h"
 #include "mozilla/StyleSheetInlines.h"
 #include "nsDocument.h"
 #include "nsStyleSheetService.h"
 
 namespace mozilla {
 
 void
 ServoStyleRuleMap::EnsureTable(ServoStyleSet& aStyleSet)
@@ -138,17 +138,17 @@ ServoStyleRuleMap::FillTableFromRule(css
     case CSSRuleBinding::SUPPORTS_RULE:
     case CSSRuleBinding::DOCUMENT_RULE: {
       auto& rule = static_cast<css::GroupRule&>(aRule);
       auto ruleList = static_cast<ServoCSSRuleList*>(rule.CssRules());
       FillTableFromRuleList(*ruleList);
       break;
     }
     case CSSRuleBinding::IMPORT_RULE: {
-      auto& rule = static_cast<ServoImportRule&>(aRule);
+      auto& rule = static_cast<CSSImportRule&>(aRule);
       MOZ_ASSERT(aRule.GetStyleSheet());
       FillTableFromStyleSheet(*rule.GetStyleSheet());
       break;
     }
   }
 }
 
 void

--- a/layout/style/CSSImportRule.cpp
+++ b/layout/style/CSSImportRule.cpp
@@ -3,20 +3,109 @@
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #include "mozilla/dom/CSSImportRule.h"
 
 #include "mozilla/dom/CSSImportRuleBinding.h"
 #include "mozilla/dom/MediaList.h"
+#include "mozilla/ServoBindings.h"
+#include "mozilla/StyleSheet.h"
 
 namespace mozilla {
 namespace dom {
 
+CSSImportRule::CSSImportRule(RefPtr<RawServoImportRule> aRawRule,
+                             uint32_t aLine,
+                             uint32_t aColumn)
+  : Rule(aLine, aColumn)
+  , mRawRule(std::move(aRawRule))
+{
+  const auto* sheet = Servo_ImportRule_GetSheet(mRawRule.get());
+  MOZ_ASSERT(sheet);
+  mChildSheet = const_cast<StyleSheet*>(sheet);
+  mChildSheet->SetOwnerRule(this);
+}
+
+CSSImportRule::~CSSImportRule()
+{
+  if (mChildSheet) {
+    mChildSheet->SetOwnerRule(nullptr);
+  }
+}
+
+// QueryInterface implementation for CSSImportRule
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(CSSImportRule)
+NS_INTERFACE_MAP_END_INHERITING(css::Rule)
+
+NS_IMPL_CYCLE_COLLECTION_CLASS(CSSImportRule)
+
+NS_IMPL_ADDREF_INHERITED(CSSImportRule, css::Rule)
+NS_IMPL_RELEASE_INHERITED(CSSImportRule, css::Rule)
+
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INHERITED(CSSImportRule,
+                                                  css::Rule)
+  // Note the child sheet twice, since the Servo rule also holds a strong
+  // reference to it.
+  NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(cb, "mChildSheet");
+  cb.NoteXPCOMChild(tmp->mChildSheet);
+  MOZ_ASSERT_IF(tmp->mRawRule,
+                Servo_ImportRule_GetSheet(tmp->mRawRule) == tmp->mChildSheet);
+  cb.NoteXPCOMChild(tmp->mChildSheet);
+  NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(cb, "mRawRule.stylesheet");
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
+
+NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(CSSImportRule)
+  if (tmp->mChildSheet) {
+    tmp->mChildSheet->SetOwnerRule(nullptr);
+    tmp->mChildSheet = nullptr;
+  }
+  tmp->mRawRule = nullptr;
+NS_IMPL_CYCLE_COLLECTION_UNLINK_END_INHERITED(css::Rule)
+
+#ifdef DEBUG
+/* virtual */ void
+CSSImportRule::List(FILE* out, int32_t aIndent) const
+{
+  nsAutoCString str;
+  for (int32_t i = 0; i < aIndent; i++) {
+    str.AppendLiteral("  ");
+  }
+  Servo_ImportRule_Debug(mRawRule, &str);
+  fprintf_stderr(out, "%s\n", str.get());
+}
+#endif
+
+dom::MediaList*
+CSSImportRule::GetMedia() const
+{
+  // When Bug 1326509 is fixed, we can assert mChildSheet instead.
+  return mChildSheet ? mChildSheet->Media() : nullptr;
+}
+
+void
+CSSImportRule::GetHref(nsAString& aHref) const
+{
+  Servo_ImportRule_GetHref(mRawRule, &aHref);
+}
+
+/* virtual */ void
+CSSImportRule::GetCssText(nsAString& aCssText) const
+{
+  Servo_ImportRule_GetCssText(mRawRule, &aCssText);
+}
+
+/* virtual */ size_t
+CSSImportRule::SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const
+{
+  // TODO Implement this!
+  return aMallocSizeOf(this);
+}
+
 bool
 CSSImportRule::IsCCLeaf() const
 {
   // We're not a leaf.
   return false;
 }
 
 /* virtual */ JSObject*

--- a/layout/style/CSSImportRule.h
+++ b/layout/style/CSSImportRule.h
@@ -5,36 +5,52 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #ifndef mozilla_dom_CSSImportRule_h
 #define mozilla_dom_CSSImportRule_h
 
 #include "mozilla/css/Rule.h"
 
 namespace mozilla {
+
+class StyleSheet;
+
 namespace dom {
 
-class CSSImportRule : public css::Rule
+class CSSImportRule final : public css::Rule
 {
-protected:
-  using Rule::Rule;
-  virtual ~CSSImportRule() {}
+public:
+  CSSImportRule(RefPtr<RawServoImportRule> aRawRule,
+                uint32_t aLine, uint32_t aColumn);
 
-public:
+  NS_DECL_ISUPPORTS_INHERITED
+  NS_DECL_CYCLE_COLLECTION_CLASS_INHERITED(CSSImportRule, css::Rule)
+
   bool IsCCLeaf() const final;
 
+#ifdef DEBUG
+  void List(FILE* out = stdout, int32_t aIndent = 0) const final;
+#endif
+
   size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf)
-    const override = 0;
+    const override;
 
   // WebIDL interface
   uint16_t Type() const final { return CSSRuleBinding::IMPORT_RULE; }
-  virtual void GetHref(nsAString& aHref) const = 0;
-  virtual dom::MediaList* GetMedia() const = 0;
-  virtual StyleSheet* GetStyleSheet() const = 0;
+  void GetCssText(nsAString& aCssText) const override;
+  void GetHref(nsAString& aHref) const;
+  dom::MediaList* GetMedia() const;
+  StyleSheet* GetStyleSheet() const { return mChildSheet; }
 
   JSObject* WrapObject(JSContext* aCx,
                        JS::Handle<JSObject*> aGivenProto) override;
+
+private:
+  ~CSSImportRule();
+
+  RefPtr<RawServoImportRule> mRawRule;
+  RefPtr<StyleSheet> mChildSheet;
 };
 
 } // namespace dom
 } // namespace mozilla
 
 #endif // mozilla_dom_CSSImportRule_h

--- a/layout/style/ServoCSSRuleList.cpp
+++ b/layout/style/ServoCSSRuleList.cpp
@@ -5,26 +5,26 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 /* representation of CSSRuleList for stylo */
 
 #include "mozilla/ServoCSSRuleList.h"
 
 #include "mozilla/dom/CSSCounterStyleRule.h"
 #include "mozilla/dom/CSSFontFaceRule.h"
+#include "mozilla/dom/CSSImportRule.h"
 #include "mozilla/dom/CSSKeyframesRule.h"
 #include "mozilla/dom/CSSMediaRule.h"
 #include "mozilla/dom/CSSMozDocumentRule.h"
 #include "mozilla/dom/CSSNamespaceRule.h"
 #include "mozilla/dom/CSSPageRule.h"
 #include "mozilla/dom/CSSStyleRule.h"
 #include "mozilla/dom/CSSSupportsRule.h"
 #include "mozilla/IntegerRange.h"
 #include "mozilla/ServoBindings.h"
-#include "mozilla/ServoImportRule.h"
 #include "mozilla/ServoFontFeatureValuesRule.h"
 #include "mozilla/StyleSheet.h"
 
 using namespace mozilla::dom;
 
 namespace mozilla {
 
 ServoCSSRuleList::ServoCSSRuleList(already_AddRefed<ServoCssRules> aRawRules,
@@ -106,17 +106,17 @@ ServoCSSRuleList::GetRule(uint32_t aInde
       }
       CASE_RULE_CSS(STYLE, Style)
       CASE_RULE_CSS(KEYFRAMES, Keyframes)
       CASE_RULE_CSS(MEDIA, Media)
       CASE_RULE_CSS(NAMESPACE, Namespace)
       CASE_RULE_CSS(PAGE, Page)
       CASE_RULE_CSS(SUPPORTS, Supports)
       CASE_RULE_CSS(DOCUMENT, MozDocument)
-      CASE_RULE(IMPORT, Import)
+      CASE_RULE_CSS(IMPORT, Import)
       CASE_RULE(FONT_FEATURE_VALUES, FontFeatureValues)
       CASE_RULE_CSS(FONT_FACE, FontFace)
       CASE_RULE_CSS(COUNTER_STYLE, CounterStyle)
 #undef CASE_RULE
       case CSSRuleBinding::KEYFRAME_RULE:
         MOZ_ASSERT_UNREACHABLE("keyframe rule cannot be here");
         return nullptr;
       default:

deleted file mode 100644
--- a/layout/style/ServoImportRule.cpp
+++ /dev/null
@@ -1,109 +0,0 @@
-/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
-/* vim: set ts=8 sts=2 et sw=2 tw=80: */
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-/* representation of CSSImportRule for stylo */
-
-#include "mozilla/ServoImportRule.h"
-
-#include "mozilla/ServoBindings.h"
-#include "mozilla/StyleSheet.h"
-
-namespace mozilla {
-
-ServoImportRule::ServoImportRule(RefPtr<RawServoImportRule> aRawRule,
-                                 uint32_t aLine,
-                                 uint32_t aColumn)
-  : CSSImportRule(aLine, aColumn)
-  , mRawRule(std::move(aRawRule))
-{
-  const auto* sheet = Servo_ImportRule_GetSheet(mRawRule.get());
-  MOZ_ASSERT(sheet);
-  mChildSheet = const_cast<StyleSheet*>(sheet);
-  mChildSheet->SetOwnerRule(this);
-}
-
-ServoImportRule::~ServoImportRule()
-{
-  if (mChildSheet) {
-    mChildSheet->SetOwnerRule(nullptr);
-  }
-}
-
-// QueryInterface implementation for ServoImportRule
-NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(ServoImportRule)
-NS_INTERFACE_MAP_END_INHERITING(dom::CSSImportRule)
-
-NS_IMPL_CYCLE_COLLECTION_CLASS(ServoImportRule)
-
-NS_IMPL_ADDREF_INHERITED(ServoImportRule, dom::CSSImportRule)
-NS_IMPL_RELEASE_INHERITED(ServoImportRule, dom::CSSImportRule)
-
-NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INHERITED(ServoImportRule,
-                                                  dom::CSSImportRule)
-  // Note the child sheet twice, since the Servo rule also holds a strong
-  // reference to it.
-  NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(cb, "mChildSheet");
-  cb.NoteXPCOMChild(tmp->mChildSheet);
-  MOZ_ASSERT_IF(tmp->mRawRule,
-                Servo_ImportRule_GetSheet(tmp->mRawRule) == tmp->mChildSheet);
-  cb.NoteXPCOMChild(tmp->mChildSheet);
-  NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(cb, "mRawRule.stylesheet");
-NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
-
-NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(ServoImportRule)
-  if (tmp->mChildSheet) {
-    tmp->mChildSheet->SetOwnerRule(nullptr);
-    tmp->mChildSheet = nullptr;
-  }
-  tmp->mRawRule = nullptr;
-NS_IMPL_CYCLE_COLLECTION_UNLINK_END_INHERITED(dom::CSSImportRule)
-
-#ifdef DEBUG
-/* virtual */ void
-ServoImportRule::List(FILE* out, int32_t aIndent) const
-{
-  nsAutoCString str;
-  for (int32_t i = 0; i < aIndent; i++) {
-    str.AppendLiteral("  ");
-  }
-  Servo_ImportRule_Debug(mRawRule, &str);
-  fprintf_stderr(out, "%s\n", str.get());
-}
-#endif
-
-dom::MediaList*
-ServoImportRule::GetMedia() const
-{
-  // When Bug 1326509 is fixed, we can assert mChildSheet instead.
-  return mChildSheet ? mChildSheet->Media() : nullptr;
-}
-
-StyleSheet*
-ServoImportRule::GetStyleSheet() const
-{
-  return mChildSheet;
-}
-
-void
-ServoImportRule::GetHref(nsAString& aHref) const
-{
-  Servo_ImportRule_GetHref(mRawRule, &aHref);
-}
-
-/* virtual */ void
-ServoImportRule::GetCssText(nsAString& aCssText) const
-{
-  Servo_ImportRule_GetCssText(mRawRule, &aCssText);
-}
-
-/* virtual */ size_t
-ServoImportRule::SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const
-{
-  // TODO Implement this!
-  return aMallocSizeOf(this);
-}
-
-} // namespace mozilla

deleted file mode 100644
--- a/layout/style/ServoImportRule.h
+++ /dev/null
@@ -1,49 +0,0 @@
-/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
-/* vim: set ts=8 sts=2 et sw=2 tw=80: */
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-/* representation of CSSImportRule for stylo */
-
-#ifndef mozilla_ServoImportRule_h
-#define mozilla_ServoImportRule_h
-
-#include "mozilla/dom/CSSImportRule.h"
-#include "mozilla/ServoBindingTypes.h"
-
-namespace mozilla {
-
-class ServoMediaList;
-class StyleSheet;
-
-class ServoImportRule final : public dom::CSSImportRule
-{
-public:
-  ServoImportRule(RefPtr<RawServoImportRule> aRawRule,
-                  uint32_t aLine, uint32_t aColumn);
-
-  NS_DECL_ISUPPORTS_INHERITED
-  NS_DECL_CYCLE_COLLECTION_CLASS_INHERITED(ServoImportRule, dom::CSSImportRule)
-
-#ifdef DEBUG
-  void List(FILE* out = stdout, int32_t aIndent = 0) const final;
-#endif
-  size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const final;
-
-  // WebIDL interface
-  void GetCssText(nsAString& aCssText) const override;
-  void GetHref(nsAString& aHref) const final;
-  dom::MediaList* GetMedia() const final;
-  StyleSheet* GetStyleSheet() const final;
-
-private:
-  ~ServoImportRule();
-
-  RefPtr<RawServoImportRule> mRawRule;
-  RefPtr<StyleSheet> mChildSheet;
-};
-
-} // namespace mozilla
-
-#endif // mozilla_ServoImportRule_h

--- a/layout/style/moz.build
+++ b/layout/style/moz.build
@@ -82,17 +82,16 @@ EXPORTS.mozilla += [
     'ServoBindingTypes.h',
     'ServoComputedData.h',
     'ServoComputedDataInlines.h',
     'ServoCSSParser.h',
     'ServoCSSRuleList.h',
     'ServoElementSnapshot.h',
     'ServoElementSnapshotTable.h',
     'ServoFontFeatureValuesRule.h',
-    'ServoImportRule.h',
     'ServoSpecifiedValues.h',
     'ServoStyleSet.h',
     'ServoStyleSetInlines.h',
     'ServoTraversalStatistics.h',
     'ServoTypes.h',
     'ServoUtils.h',
     'SheetType.h',
     'StyleAnimationValue.h',
@@ -198,17 +197,16 @@ UNIFIED_SOURCES += [
     'PostTraversalTask.cpp',
     'PreloadedStyleSheet.cpp',
     'Rule.cpp',
     'ServoBindings.cpp',
     'ServoCSSParser.cpp',
     'ServoCSSRuleList.cpp',
     'ServoElementSnapshot.cpp',
     'ServoFontFeatureValuesRule.cpp',
-    'ServoImportRule.cpp',
     'ServoSpecifiedValues.cpp',
     'ServoStyleSet.cpp',
     'StreamLoader.cpp',
     'StyleAnimationValue.cpp',
     'StyleComplexColor.cpp',
     'StyleSheet.cpp',
     'URLExtraData.cpp',
 ]

--- a/layout/style/nsCSSProps.cpp
+++ b/layout/style/nsCSSProps.cpp
@@ -15,16 +15,17 @@
 #include "mozilla/Casting.h"
 
 #include "nsCSSKeywords.h"
 #include "nsLayoutUtils.h"
 #include "nsStyleConsts.h"
 #include "nsIWidget.h"
 #include "nsThemeConstants.h"  // For system widget appearance types
 
+#include "mozilla/dom/Animation.h"
 #include "mozilla/dom/AnimationEffectBinding.h" // for PlaybackDirection
 #include "mozilla/LookAndFeel.h" // for system colors
 
 #include "nsString.h"
 #include "nsStaticNameTable.h"
 
 #include "mozilla/Preferences.h"
 #include "mozilla/StaticPrefs.h"

--- a/layout/style/nsDOMCSSRect.h
+++ b/layout/style/nsDOMCSSRect.h
@@ -9,17 +9,17 @@
 #ifndef nsDOMCSSRect_h_
 #define nsDOMCSSRect_h_
 
 #include "mozilla/Attributes.h"
 #include "mozilla/RefPtr.h"
 
 class nsROCSSPrimitiveValue;
 
-class nsDOMCSSRect final : public RefCounted<nsDOMCSSRect>
+class nsDOMCSSRect final : public mozilla::RefCounted<nsDOMCSSRect>
 {
 public:
   MOZ_DECLARE_REFCOUNTED_TYPENAME(nsDOMCSSRect);
 
   nsDOMCSSRect(nsROCSSPrimitiveValue* aTop,
                nsROCSSPrimitiveValue* aRight,
                nsROCSSPrimitiveValue* aBottom,
                nsROCSSPrimitiveValue* aLeft);