--- a/dom/base/nsAttrAndChildArray.cpp
+++ b/dom/base/nsAttrAndChildArray.cpp
@@ -716,16 +716,24 @@ nsAttrAndChildArray::NonMappedAttrCount(
 }
 
 uint32_t
 nsAttrAndChildArray::MappedAttrCount() const
 {
   return mImpl && mImpl->mMappedAttrs ? (uint32_t)mImpl->mMappedAttrs->Count() : 0;
 }
 
+nsresult
+nsAttrAndChildArray::ForceMapped(nsMappedAttributeElement* aContent, nsIDocument* aDocument)
+{
+  nsHTMLStyleSheet* sheet = aDocument->GetAttributeStyleSheet();
+  nsMappedAttributes* mapped = GetModifiableMapped(aContent, sheet, false);
+  return MakeMappedUnique(mapped);
+}
+
 nsMappedAttributes*
 nsAttrAndChildArray::GetModifiableMapped(nsMappedAttributeElement* aContent,
                                          nsHTMLStyleSheet* aSheet,
                                          bool aWillAddAttr)
 {
   if (mImpl && mImpl->mMappedAttrs) {
     return mImpl->mMappedAttrs->Clone(aWillAddAttr);
   }

--- a/dom/base/nsAttrAndChildArray.h
+++ b/dom/base/nsAttrAndChildArray.h
@@ -131,16 +131,19 @@ public:
 
   size_t SizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf) const;
   bool HasMappedAttrs() const
   {
     return MappedAttrCount();
   }
   const nsMappedAttributes* GetMapped() const;
 
+  // Force this to have mapped attributes, even if those attributes are empty.
+  nsresult ForceMapped(nsMappedAttributeElement* aContent, nsIDocument* aDocument);
+
 private:
   nsAttrAndChildArray(const nsAttrAndChildArray& aOther) = delete;
   nsAttrAndChildArray& operator=(const nsAttrAndChildArray& aOther) = delete;
 
   void Clear();
 
   uint32_t NonMappedAttrCount() const;
   uint32_t MappedAttrCount() const;

--- a/dom/base/nsFrameLoader.cpp
+++ b/dom/base/nsFrameLoader.cpp
@@ -50,16 +50,17 @@
 #include "nsIEditor.h"
 #include "nsIMozBrowserFrame.h"
 #include "nsISHistory.h"
 #include "NullPrincipal.h"
 #include "nsIScriptError.h"
 #include "nsGlobalWindow.h"
 #include "nsPIWindowRoot.h"
 #include "nsLayoutUtils.h"
+#include "nsMappedAttributes.h"
 #include "nsView.h"
 #include "GroupedSHistory.h"
 #include "PartialSHistory.h"
 
 #include "nsIURI.h"
 #include "nsIURL.h"
 #include "nsNetUtil.h"
 
@@ -1198,16 +1199,28 @@ nsFrameLoader::MarginsChanged(uint32_t a
   // margins.
   if (!mDocShell)
     return;
 
   // Set the margins
   mDocShell->SetMarginWidth(aMarginWidth);
   mDocShell->SetMarginHeight(aMarginHeight);
 
+  // There's a cached property declaration block
+  // that needs to be updated
+  if (nsIDocument* doc = mDocShell->GetDocument()) {
+    if (doc->GetStyleBackendType() == StyleBackendType::Servo) {
+      for (nsINode* cur = doc; cur; cur = cur->GetNextNode()) {
+        if (cur->IsHTMLElement(nsGkAtoms::body)) {
+          static_cast<HTMLBodyElement*>(cur)->GetMappedAttributes()->ClearServoStyle();
+        }
+      }
+    }
+  }
+
   // Trigger a restyle if there's a prescontext
   // FIXME: This could do something much less expensive.
   RefPtr<nsPresContext> presContext;
   mDocShell->GetPresContext(getter_AddRefs(presContext));
   if (presContext)
     presContext->RebuildAllStyleData(nsChangeHint(0), eRestyle_Subtree);
 }
 

--- a/dom/base/nsMappedAttributes.h
+++ b/dom/base/nsMappedAttributes.h
@@ -79,16 +79,24 @@ public:
   // Obtain the contained servo declaration block
   // May return null if called before the inner block
   // has been (lazily) resolved
   const RefPtr<RawServoDeclarationBlock>& GetServoStyle() const
   {
     return mServoStyle;
   }
 
+  void ClearServoStyle() const {
+    // The servo style is lazily resolved, so it's fine to
+    // clear it on the main thread even in a shared nsMappedAttributes
+    // object
+    nsMappedAttributes* self = const_cast<nsMappedAttributes*>(this);
+    self->mServoStyle = nullptr;
+  }
+
   // nsIStyleRule
   virtual void MapRuleInfoInto(nsRuleData* aRuleData) override;
   virtual bool MightMapInheritedStyleData() override;
   virtual bool GetDiscretelyAnimatedCSSValue(nsCSSPropertyID aProperty,
                                              nsCSSValue* aValue) override;
 #ifdef DEBUG
   virtual void List(FILE* out = stdout, int32_t aIndent = 0) const override;
 #endif

--- a/dom/html/HTMLBodyElement.cpp
+++ b/dom/html/HTMLBodyElement.cpp
@@ -22,192 +22,16 @@
 
 NS_IMPL_NS_NEW_HTML_ELEMENT(Body)
 
 namespace mozilla {
 namespace dom {
 
 //----------------------------------------------------------------------
 
-BodyRule::BodyRule(HTMLBodyElement* aPart)
-  : mPart(aPart)
-{
-}
-
-BodyRule::~BodyRule()
-{
-}
-
-NS_IMPL_ISUPPORTS(BodyRule, nsIStyleRule)
-
-/* virtual */ void
-BodyRule::MapRuleInfoInto(nsRuleData* aData)
-{
-  if (!(aData->mSIDs & NS_STYLE_INHERIT_BIT(Margin)) || !mPart)
-    return; // We only care about margins.
-
-  int32_t bodyMarginWidth  = -1;
-  int32_t bodyMarginHeight = -1;
-  int32_t bodyTopMargin = -1;
-  int32_t bodyBottomMargin = -1;
-  int32_t bodyLeftMargin = -1;
-  int32_t bodyRightMargin = -1;
-
-  // check the mode (fortunately, the ruleData has a presContext for us to use!)
-  NS_ASSERTION(aData->mPresContext, "null presContext in ruleNode was unexpected");
-  nsCompatibility mode = aData->mPresContext->CompatibilityMode();
-
-
-  const nsAttrValue* value;
-  if (mPart->GetAttrCount() > 0) {
-    // if marginwidth/marginheight are set, reflect them as 'margin'
-    value = mPart->GetParsedAttr(nsGkAtoms::marginwidth);
-    if (value && value->Type() == nsAttrValue::eInteger) {
-      bodyMarginWidth = value->GetIntegerValue();
-      if (bodyMarginWidth < 0) bodyMarginWidth = 0;
-      nsCSSValue* marginLeft = aData->ValueForMarginLeft();
-      if (marginLeft->GetUnit() == eCSSUnit_Null)
-        marginLeft->SetFloatValue((float)bodyMarginWidth, eCSSUnit_Pixel);
-      nsCSSValue* marginRight = aData->ValueForMarginRight();
-      if (marginRight->GetUnit() == eCSSUnit_Null)
-        marginRight->SetFloatValue((float)bodyMarginWidth, eCSSUnit_Pixel);
-    }
-
-    value = mPart->GetParsedAttr(nsGkAtoms::marginheight);
-    if (value && value->Type() == nsAttrValue::eInteger) {
-      bodyMarginHeight = value->GetIntegerValue();
-      if (bodyMarginHeight < 0) bodyMarginHeight = 0;
-      nsCSSValue* marginTop = aData->ValueForMarginTop();
-      if (marginTop->GetUnit() == eCSSUnit_Null)
-        marginTop->SetFloatValue((float)bodyMarginHeight, eCSSUnit_Pixel);
-      nsCSSValue* marginBottom = aData->ValueForMarginBottom();
-      if (marginBottom->GetUnit() == eCSSUnit_Null)
-        marginBottom->SetFloatValue((float)bodyMarginHeight, eCSSUnit_Pixel);
-    }
-
-      // topmargin (IE-attribute)
-    value = mPart->GetParsedAttr(nsGkAtoms::topmargin);
-    if (value && value->Type() == nsAttrValue::eInteger) {
-      bodyTopMargin = value->GetIntegerValue();
-      if (bodyTopMargin < 0) bodyTopMargin = 0;
-      nsCSSValue* marginTop = aData->ValueForMarginTop();
-      if (marginTop->GetUnit() == eCSSUnit_Null)
-        marginTop->SetFloatValue((float)bodyTopMargin, eCSSUnit_Pixel);
-    }
-
-      // bottommargin (IE-attribute)
-    value = mPart->GetParsedAttr(nsGkAtoms::bottommargin);
-    if (value && value->Type() == nsAttrValue::eInteger) {
-      bodyBottomMargin = value->GetIntegerValue();
-      if (bodyBottomMargin < 0) bodyBottomMargin = 0;
-      nsCSSValue* marginBottom = aData->ValueForMarginBottom();
-      if (marginBottom->GetUnit() == eCSSUnit_Null)
-        marginBottom->SetFloatValue((float)bodyBottomMargin, eCSSUnit_Pixel);
-    }
-
-      // leftmargin (IE-attribute)
-    value = mPart->GetParsedAttr(nsGkAtoms::leftmargin);
-    if (value && value->Type() == nsAttrValue::eInteger) {
-      bodyLeftMargin = value->GetIntegerValue();
-      if (bodyLeftMargin < 0) bodyLeftMargin = 0;
-      nsCSSValue* marginLeft = aData->ValueForMarginLeft();
-      if (marginLeft->GetUnit() == eCSSUnit_Null)
-        marginLeft->SetFloatValue((float)bodyLeftMargin, eCSSUnit_Pixel);
-    }
-
-      // rightmargin (IE-attribute)
-    value = mPart->GetParsedAttr(nsGkAtoms::rightmargin);
-    if (value && value->Type() == nsAttrValue::eInteger) {
-      bodyRightMargin = value->GetIntegerValue();
-      if (bodyRightMargin < 0) bodyRightMargin = 0;
-      nsCSSValue* marginRight = aData->ValueForMarginRight();
-      if (marginRight->GetUnit() == eCSSUnit_Null)
-        marginRight->SetFloatValue((float)bodyRightMargin, eCSSUnit_Pixel);
-    }
-
-  }
-
-  // if marginwidth or marginheight is set in the <frame> and not set in the <body>
-  // reflect them as margin in the <body>
-  if (bodyMarginWidth == -1 || bodyMarginHeight == -1) {
-    nsCOMPtr<nsIDocShell> docShell(aData->mPresContext->GetDocShell());
-    if (docShell) {
-      nscoord frameMarginWidth=-1;  // default value
-      nscoord frameMarginHeight=-1; // default value
-      docShell->GetMarginWidth(&frameMarginWidth); // -1 indicates not set
-      docShell->GetMarginHeight(&frameMarginHeight);
-      if ((frameMarginWidth >= 0) && (bodyMarginWidth == -1)) { // set in <frame> & not in <body>
-        if (eCompatibility_NavQuirks == mode) {
-          if ((bodyMarginHeight == -1) && (0 > frameMarginHeight)) // nav quirk
-            frameMarginHeight = 0;
-        }
-      }
-      if ((frameMarginHeight >= 0) && (bodyMarginHeight == -1)) { // set in <frame> & not in <body>
-        if (eCompatibility_NavQuirks == mode) {
-          if ((bodyMarginWidth == -1) && (0 > frameMarginWidth)) // nav quirk
-            frameMarginWidth = 0;
-        }
-      }
-
-      if ((bodyMarginWidth == -1) && (frameMarginWidth >= 0)) {
-        nsCSSValue* marginLeft = aData->ValueForMarginLeft();
-        if (marginLeft->GetUnit() == eCSSUnit_Null)
-          marginLeft->SetFloatValue((float)frameMarginWidth, eCSSUnit_Pixel);
-        nsCSSValue* marginRight = aData->ValueForMarginRight();
-        if (marginRight->GetUnit() == eCSSUnit_Null)
-          marginRight->SetFloatValue((float)frameMarginWidth, eCSSUnit_Pixel);
-      }
-
-      if ((bodyMarginHeight == -1) && (frameMarginHeight >= 0)) {
-        nsCSSValue* marginTop = aData->ValueForMarginTop();
-        if (marginTop->GetUnit() == eCSSUnit_Null)
-          marginTop->SetFloatValue((float)frameMarginHeight, eCSSUnit_Pixel);
-        nsCSSValue* marginBottom = aData->ValueForMarginBottom();
-        if (marginBottom->GetUnit() == eCSSUnit_Null)
-          marginBottom->SetFloatValue((float)frameMarginHeight, eCSSUnit_Pixel);
-      }
-    }
-  }
-}
-
-/* virtual */ bool
-BodyRule::MightMapInheritedStyleData()
-{
-  return false;
-}
-
-/* virtual */ bool
-BodyRule::GetDiscretelyAnimatedCSSValue(nsCSSPropertyID aProperty,
-                                        nsCSSValue* aValue)
-{
-  MOZ_ASSERT(false, "GetDiscretelyAnimatedCSSValue is not implemented yet");
-  return false;
-}
-
-#ifdef DEBUG
-/* virtual */ void
-BodyRule::List(FILE* out, int32_t aIndent) const
-{
-  nsAutoCString indent;
-  for (int32_t index = aIndent; --index >= 0; ) {
-    indent.AppendLiteral("  ");
-  }
-  fprintf_stderr(out, "%s[body rule] {}\n", indent.get());
-}
-#endif
-
-//----------------------------------------------------------------------
-
-HTMLBodyElement::~HTMLBodyElement()
-{
-  if (mContentStyleRule) {
-    mContentStyleRule->mPart = nullptr;
-  }
-}
-
 JSObject*
 HTMLBodyElement::WrapNode(JSContext *aCx, JS::Handle<JSObject*> aGivenProto)
 {
   return HTMLBodyElementBinding::Wrap(aCx, this, aGivenProto);
 }
 
 NS_IMPL_ISUPPORTS_INHERITED(HTMLBodyElement, nsGenericHTMLElement,
                             nsIDOMHTMLBodyElement)
@@ -343,30 +167,118 @@ HTMLBodyElement::ParseAttribute(int32_t 
   return nsGenericHTMLElement::ParseBackgroundAttribute(aNamespaceID,
                                                         aAttribute, aValue,
                                                         aResult) ||
          nsGenericHTMLElement::ParseAttribute(aNamespaceID, aAttribute, aValue,
                                               aResult);
 }
 
 void
-HTMLBodyElement::UnbindFromTree(bool aDeep, bool aNullParent)
-{
-  if (mContentStyleRule) {
-    mContentStyleRule->mPart = nullptr;
-    mContentStyleRule = nullptr;
-  }
-
-  nsGenericHTMLElement::UnbindFromTree(aDeep, aNullParent);  
-}
-
-void
 HTMLBodyElement::MapAttributesIntoRule(const nsMappedAttributes* aAttributes,
                                        GenericSpecifiedValues* aData)
 {
+  if (!(aData->mSIDs & NS_STYLE_INHERIT_BIT(Margin)))
+    return; // We only care about margins.
+
+  int32_t bodyMarginWidth  = -1;
+  int32_t bodyMarginHeight = -1;
+  int32_t bodyTopMargin = -1;
+  int32_t bodyBottomMargin = -1;
+  int32_t bodyLeftMargin = -1;
+  int32_t bodyRightMargin = -1;
+
+  // check the mode (fortunately, the ruleData has a presContext for us to use!)
+  NS_ASSERTION(aData->mPresContext, "null presContext in ruleNode was unexpected");
+  nsCompatibility mode = aData->mPresContext->CompatibilityMode();
+
+
+  const nsAttrValue* value;
+  // if marginwidth/marginheight are set, reflect them as 'margin'
+  value = aAttributes->GetAttr(nsGkAtoms::marginwidth);
+  if (value && value->Type() == nsAttrValue::eInteger) {
+    bodyMarginWidth = value->GetIntegerValue();
+    if (bodyMarginWidth < 0) bodyMarginWidth = 0;
+    aData->SetPixelValueIfUnset(eCSSProperty_margin_left, (float)bodyMarginWidth);
+    aData->SetPixelValueIfUnset(eCSSProperty_margin_right, (float)bodyMarginWidth);
+  }
+
+  value = aAttributes->GetAttr(nsGkAtoms::marginheight);
+  if (value && value->Type() == nsAttrValue::eInteger) {
+    bodyMarginHeight = value->GetIntegerValue();
+    if (bodyMarginHeight < 0) bodyMarginHeight = 0;
+    aData->SetPixelValueIfUnset(eCSSProperty_margin_top, (float)bodyMarginHeight);
+    aData->SetPixelValueIfUnset(eCSSProperty_margin_bottom, (float)bodyMarginHeight);
+  }
+
+    // topmargin (IE-attribute)
+  value = aAttributes->GetAttr(nsGkAtoms::topmargin);
+  if (value && value->Type() == nsAttrValue::eInteger) {
+    bodyTopMargin = value->GetIntegerValue();
+    if (bodyTopMargin < 0) bodyTopMargin = 0;
+    aData->SetPixelValueIfUnset(eCSSProperty_margin_top, (float)bodyTopMargin);
+  }
+
+    // bottommargin (IE-attribute)
+  value = aAttributes->GetAttr(nsGkAtoms::bottommargin);
+  if (value && value->Type() == nsAttrValue::eInteger) {
+    bodyBottomMargin = value->GetIntegerValue();
+    if (bodyBottomMargin < 0) bodyBottomMargin = 0;
+    aData->SetPixelValueIfUnset(eCSSProperty_margin_bottom, (float)bodyBottomMargin);
+  }
+
+    // leftmargin (IE-attribute)
+  value = aAttributes->GetAttr(nsGkAtoms::leftmargin);
+  if (value && value->Type() == nsAttrValue::eInteger) {
+    bodyLeftMargin = value->GetIntegerValue();
+    if (bodyLeftMargin < 0) bodyLeftMargin = 0;
+    aData->SetPixelValueIfUnset(eCSSProperty_margin_left, (float)bodyLeftMargin);
+  }
+
+    // rightmargin (IE-attribute)
+  value = aAttributes->GetAttr(nsGkAtoms::rightmargin);
+  if (value && value->Type() == nsAttrValue::eInteger) {
+    bodyRightMargin = value->GetIntegerValue();
+    if (bodyRightMargin < 0) bodyRightMargin = 0;
+    aData->SetPixelValueIfUnset(eCSSProperty_margin_right, (float)bodyRightMargin);
+  }
+
+  // if marginwidth or marginheight is set in the <frame> and not set in the <body>
+  // reflect them as margin in the <body>
+  if (bodyMarginWidth == -1 || bodyMarginHeight == -1) {
+    nsCOMPtr<nsIDocShell> docShell(aData->mPresContext->GetDocShell());
+    if (docShell) {
+      nscoord frameMarginWidth=-1;  // default value
+      nscoord frameMarginHeight=-1; // default value
+      docShell->GetMarginWidth(&frameMarginWidth); // -1 indicates not set
+      docShell->GetMarginHeight(&frameMarginHeight);
+      if ((frameMarginWidth >= 0) && (bodyMarginWidth == -1)) { // set in <frame> & not in <body>
+        if (eCompatibility_NavQuirks == mode) {
+          if ((bodyMarginHeight == -1) && (0 > frameMarginHeight)) // nav quirk
+            frameMarginHeight = 0;
+        }
+      }
+      if ((frameMarginHeight >= 0) && (bodyMarginHeight == -1)) { // set in <frame> & not in <body>
+        if (eCompatibility_NavQuirks == mode) {
+          if ((bodyMarginWidth == -1) && (0 > frameMarginWidth)) // nav quirk
+            frameMarginWidth = 0;
+        }
+      }
+
+      if ((bodyMarginWidth == -1) && (frameMarginWidth >= 0)) {
+        aData->SetPixelValueIfUnset(eCSSProperty_margin_left, (float)frameMarginWidth);
+        aData->SetPixelValueIfUnset(eCSSProperty_margin_right, (float)frameMarginWidth);
+      }
+
+      if ((bodyMarginHeight == -1) && (frameMarginHeight >= 0)) {
+      aData->SetPixelValueIfUnset(eCSSProperty_margin_top, (float)frameMarginHeight);
+      aData->SetPixelValueIfUnset(eCSSProperty_margin_bottom, (float)frameMarginHeight);
+      }
+    }
+  }
+
   if (aData->ShouldComputeStyleStruct(NS_STYLE_INHERIT_BIT(Display))) {
     // When display if first asked for, go ahead and get our colors set up.
     nsIPresShell *presShell = aData->PresContext()->GetPresShell();
     if (presShell) {
       nsIDocument *doc = presShell->GetDocument();
       if (doc) {
         nsHTMLStyleSheet* styleSheet = doc->GetAttributeStyleSheet();
         if (styleSheet) {
@@ -407,44 +319,24 @@ HTMLBodyElement::MapAttributesIntoRule(c
 }
 
 nsMapRuleToAttributesFunc
 HTMLBodyElement::GetAttributeMappingFunction() const
 {
   return &MapAttributesIntoRule;
 }
 
-NS_IMETHODIMP
-HTMLBodyElement::WalkContentStyleRules(nsRuleWalker* aRuleWalker)
-{
-  nsGenericHTMLElement::WalkContentStyleRules(aRuleWalker);
-
-  if (!mContentStyleRule && IsInUncomposedDoc()) {
-    // XXXbz should this use OwnerDoc() or GetComposedDoc()?
-    // sXBL/XBL2 issue!
-    mContentStyleRule = new BodyRule(this);
-  }
-  if (aRuleWalker && mContentStyleRule) {
-    aRuleWalker->Forward(mContentStyleRule);
-  }
-  return NS_OK;
-}
-
 NS_IMETHODIMP_(bool)
 HTMLBodyElement::IsAttributeMapped(const nsIAtom* aAttribute) const
 {
   static const MappedAttributeEntry attributes[] = {
     { &nsGkAtoms::link },
     { &nsGkAtoms::vlink },
     { &nsGkAtoms::alink },
     { &nsGkAtoms::text },
-    // These aren't mapped through attribute mapping, but they are
-    // mapped through a style rule, so it is attribute dependent style.
-    // XXXldb But we don't actually replace the body rule when we have
-    // dynamic changes...
     { &nsGkAtoms::marginwidth },
     { &nsGkAtoms::marginheight },
     { nullptr },
   };
 
   static const MappedAttributeEntry* const map[] = {
     attributes,
     sCommonAttributeMap,
@@ -485,16 +377,53 @@ HTMLBodyElement::GetAssociatedEditor()
 bool
 HTMLBodyElement::IsEventAttributeName(nsIAtom *aName)
 {
   return nsContentUtils::IsEventAttributeName(aName,
                                               EventNameType_HTML |
                                               EventNameType_HTMLBodyOrFramesetOnly);
 }
 
+nsresult
+HTMLBodyElement::BindToTree(nsIDocument* aDocument, nsIContent* aParent,
+                            nsIContent* aBindingParent,
+                            bool aCompileEventHandlers)
+{
+  nsresult rv = nsGenericHTMLElement::BindToTree(aDocument, aParent,
+                                                 aBindingParent,
+                                                 aCompileEventHandlers);
+  NS_ENSURE_SUCCESS(rv, rv);
+  return mAttrsAndChildren.ForceMapped(this, OwnerDoc());
+}
+
+nsresult
+HTMLBodyElement::AfterSetAttr(int32_t aNameSpaceID, nsIAtom* aName,
+                              const nsAttrValue* aValue,
+                              bool aNotify)
+{
+  nsresult rv = nsGenericHTMLElement::AfterSetAttr(aNameSpaceID,
+                                                   aName, aValue, aNotify);
+  NS_ENSURE_SUCCESS(rv, rv);
+  if (aNameSpaceID == kNameSpaceID_None) {
+    if (aName == nsGkAtoms::marginheight ||
+        aName == nsGkAtoms::marginheight ||
+        aName == nsGkAtoms::marginwidth ||
+        aName == nsGkAtoms::topmargin ||
+        aName == nsGkAtoms::rightmargin ||
+        aName == nsGkAtoms::bottommargin ||
+        aName == nsGkAtoms::leftmargin) {
+
+      nsresult rv = mAttrsAndChildren.ForceMapped(this, OwnerDoc());
+      NS_ENSURE_SUCCESS(rv, rv);
+    }
+  }
+
+  return NS_OK;
+}
+
 #define EVENT(name_, id_, type_, struct_) /* nothing; handled by the superclass */
 // nsGenericHTMLElement::GetOnError returns
 // already_AddRefed<EventHandlerNonNull> while other getters return
 // EventHandlerNonNull*, so allow passing in the type to use here.
 #define WINDOW_EVENT_HELPER(name_, type_)                                      \
   type_*                                                                       \
   HTMLBodyElement::GetOn##name_()                                              \
   {                                                                            \

--- a/dom/html/HTMLBodyElement.h
+++ b/dom/html/HTMLBodyElement.h
@@ -10,38 +10,16 @@
 #include "nsGenericHTMLElement.h"
 #include "nsIDOMHTMLBodyElement.h"
 #include "nsIStyleRule.h"
 
 namespace mozilla {
 namespace dom {
 
 class OnBeforeUnloadEventHandlerNonNull;
-class HTMLBodyElement;
-
-class BodyRule: public nsIStyleRule
-{
-  virtual ~BodyRule();
-
-public:
-  explicit BodyRule(HTMLBodyElement* aPart);
-
-  NS_DECL_ISUPPORTS
-
-  // nsIStyleRule interface
-  virtual void MapRuleInfoInto(nsRuleData* aRuleData) override;
-  virtual bool MightMapInheritedStyleData() override;
-  virtual bool GetDiscretelyAnimatedCSSValue(nsCSSPropertyID aProperty,
-                                             nsCSSValue* aValue) override;
-#ifdef DEBUG
-  virtual void List(FILE* out = stdout, int32_t aIndent = 0) const override;
-#endif
-
-  HTMLBodyElement*  mPart;  // not ref-counted, cleared by content 
-};
 
 class HTMLBodyElement final : public nsGenericHTMLElement,
                               public nsIDOMHTMLBodyElement
 {
 public:
   using Element::GetText;
   using Element::SetText;
 
@@ -120,33 +98,38 @@ public:
   {
     SetHTMLAttr(nsGkAtoms::background, aBackground, aError);
   }
 
   virtual bool ParseAttribute(int32_t aNamespaceID,
                               nsIAtom* aAttribute,
                               const nsAString& aValue,
                               nsAttrValue& aResult) override;
-  virtual void UnbindFromTree(bool aDeep = true,
-                              bool aNullParent = true) override;
   virtual nsMapRuleToAttributesFunc GetAttributeMappingFunction() const override;
-  NS_IMETHOD WalkContentStyleRules(nsRuleWalker* aRuleWalker) override;
   NS_IMETHOD_(bool) IsAttributeMapped(const nsIAtom* aAttribute) const override;
   virtual already_AddRefed<nsIEditor> GetAssociatedEditor() override;
   virtual nsresult Clone(mozilla::dom::NodeInfo *aNodeInfo, nsINode **aResult) const override;
 
   virtual bool IsEventAttributeName(nsIAtom* aName) override;
 
+
+  virtual nsresult BindToTree(nsIDocument* aDocument, nsIContent* aParent,
+                              nsIContent* aBindingParent,
+                              bool aCompileEventHandlers) override;
+  /**
+   * Called when an attribute has just been changed
+   */
+  virtual nsresult AfterSetAttr(int32_t aNameSpaceID, nsIAtom* aName,
+                                const nsAttrValue* aValue, bool aNotify) override;
+
 protected:
-  virtual ~HTMLBodyElement();
+  virtual ~HTMLBodyElement() {}
 
   virtual JSObject* WrapNode(JSContext *aCx, JS::Handle<JSObject*> aGivenProto) override;
 
-  RefPtr<BodyRule> mContentStyleRule;
-
 private:
   static void MapAttributesIntoRule(const nsMappedAttributes* aAttributes,
                                     GenericSpecifiedValues* aGenericData);
 };
 
 } // namespace dom
 } // namespace mozilla