--- a/dom/html/HTMLImageElement.cpp
+++ b/dom/html/HTMLImageElement.cpp
@@ -1195,59 +1195,50 @@ HTMLImageElement::SourceElementMatches(n
       !SupportedPictureSourceType(type)) {
     return false;
   }
 
   return true;
 }
 
 bool
-HTMLImageElement::TryCreateResponsiveSelector(nsIContent *aSourceNode,
-                                              const nsAString *aSrcset,
-                                              const nsAString *aSizes)
+HTMLImageElement::TryCreateResponsiveSelector(nsIContent *aSourceNode)
 {
   // Skip if this is not a <source> with matching media query
   bool isSourceTag = aSourceNode->IsHTMLElement(nsGkAtoms::source);
   if (isSourceTag) {
     if (!SourceElementMatches(aSourceNode)) {
       return false;
     }
   } else if (aSourceNode->IsHTMLElement(nsGkAtoms::img)) {
     // Otherwise this is the <img> tag itself
     MOZ_ASSERT(aSourceNode == this);
   }
 
   // Skip if has no srcset or an empty srcset
   nsString srcset;
-  if (aSrcset) {
-    srcset = *aSrcset;
-  } else if (!aSourceNode->GetAttr(kNameSpaceID_None, nsGkAtoms::srcset,
-                                   srcset)) {
+  if (!aSourceNode->GetAttr(kNameSpaceID_None, nsGkAtoms::srcset, srcset)) {
     return false;
   }
 
   if (srcset.IsEmpty()) {
     return false;
   }
 
 
   // Try to parse
   RefPtr<ResponsiveImageSelector> sel = new ResponsiveImageSelector(aSourceNode);
   if (!sel->SetCandidatesFromSourceSet(srcset)) {
     // No possible candidates, don't need to bother parsing sizes
     return false;
   }
 
-  if (aSizes) {
-    sel->SetSizesFromDescriptor(*aSizes);
-  } else {
-    nsAutoString sizes;
-    aSourceNode->GetAttr(kNameSpaceID_None, nsGkAtoms::sizes, sizes);
-    sel->SetSizesFromDescriptor(sizes);
-  }
+  nsAutoString sizes;
+  aSourceNode->GetAttr(kNameSpaceID_None, nsGkAtoms::sizes, sizes);
+  sel->SetSizesFromDescriptor(sizes);
 
   // If this is the <img> tag, also pull in src as the default source
   if (!isSourceTag) {
     MOZ_ASSERT(aSourceNode == this);
     nsAutoString src;
     if (GetAttr(kNameSpaceID_None, nsGkAtoms::src, src) && !src.IsEmpty()) {
       sel->SetDefaultSource(src);
     }

--- a/dom/html/HTMLImageElement.h
+++ b/dom/html/HTMLImageElement.h
@@ -326,19 +326,17 @@ protected:
   bool UpdateResponsiveSource();
 
   // Given a <source> node that is a previous sibling *or* ourselves, try to
   // create a ResponsiveSelector.
 
   // If the node's srcset/sizes make for an invalid selector, returns
   // false. This does not guarantee the resulting selector matches an image,
   // only that it is valid.
-  bool TryCreateResponsiveSelector(nsIContent *aSourceNode,
-                                   const nsAString *aSrcset = nullptr,
-                                   const nsAString *aSizes = nullptr);
+  bool TryCreateResponsiveSelector(nsIContent *aSourceNode);
 
   CSSIntPoint GetXY();
   virtual JSObject* WrapNode(JSContext *aCx, JS::Handle<JSObject*> aGivenProto) override;
   void UpdateFormOwner();
 
   virtual nsresult BeforeSetAttr(int32_t aNameSpaceID, nsIAtom* aName,
                                  nsAttrValueOrString* aValue,
                                  bool aNotify) override;