Bug 1329093 - Part 3: Overload FromContent() to work with const; r=bz

MozReview-Commit-ID: BUFmPtcf6LM

dom/base/nsIContent.h

@@ -1037,7 +1037,15 @@ inline nsIContent* nsINode::AsContent()
   {                                                                            \
     return aContent->_check ? static_cast<_class*>(aContent) : nullptr;        \
   }                                                                            \
+  static const _class* FromContent(const nsIContent* aContent)                 \
+  {                                                                            \
+    return aContent->_check ? static_cast<const _class*>(aContent) : nullptr;  \
+  }                                                                            \
   static _class* FromContentOrNull(nsIContent* aContent)                       \
+  {                                                                            \
+    return aContent ? FromContent(aContent) : nullptr;                         \
+  }                                                                            \
+  static const _class* FromContentOrNull(const nsIContent* aContent)           \
   {                                                                            \
     return aContent ? FromContent(aContent) : nullptr;                         \
   }

layout/style/ServoBindings.cpp

@@ -373,7 +373,7 @@ Gecko_GetHTMLPresentationAttrDeclarationBlock(RawGeckoElementBorrowed aElement)
                 "RefPtr should just be a pointer");
   const nsMappedAttributes* attrs = aElement->GetMappedAttributes();
   if (!attrs) {
-    auto* svg = nsSVGElement::FromContentOrNull(const_cast<dom::Element*>(aElement));
+    auto* svg = nsSVGElement::FromContentOrNull(aElement);
     if (svg) {
       if (auto decl = svg->GetContentDeclarationBlock()) {
         return decl->AsServo()->RefRawStrong();