--- a/dom/base/nsTreeSanitizer.cpp
+++ b/dom/base/nsTreeSanitizer.cpp
@@ -990,17 +990,17 @@ nsTreeSanitizer::MustFlatten(int32_t aNa
   }
   if (aNamespace == kNameSpaceID_MathML) {
     return !sElementsMathML->GetEntry(aLocal);
   }
   return true;
 }
 
 bool
-nsTreeSanitizer::IsURL(nsAtom*** aURLs, nsAtom* aLocalName)
+nsTreeSanitizer::IsURL(nsAtom** const* aURLs, nsAtom* aLocalName)
 {
   nsAtom** atomPtrPtr;
   while ((atomPtrPtr = *aURLs)) {
     if (*atomPtrPtr == aLocalName) {
       return true;
     }
     ++aURLs;
   }
@@ -1158,17 +1158,17 @@ nsTreeSanitizer::SanitizeStyleSheet(cons
     }
   }
   return didSanitize;
 }
 
 void
 nsTreeSanitizer::SanitizeAttributes(mozilla::dom::Element* aElement,
                                     nsTHashtable<nsRefPtrHashKey<nsAtom>>* aAllowed,
-                                    nsAtom*** aURLs,
+                                    nsAtom** const* aURLs,
                                     bool aAllowXLink,
                                     bool aAllowStyle,
                                     bool aAllowDangerousSrc)
 {
   uint32_t ac = aElement->GetAttrCount();
 
   for (int32_t i = ac - 1; i >= 0; --i) {
     const nsAttrName* attrName = aElement->GetAttrNameAt(i);
@@ -1423,24 +1423,24 @@ nsTreeSanitizer::SanitizeChildren(nsINod
           nsContentUtils::SetNodeTextContent(node, sanitizedStyle, true);
         } else {
           // If the node had non-text child nodes, this operation zaps those.
           nsContentUtils::SetNodeTextContent(node, styleText, true);
         }
         if (ns == kNameSpaceID_XHTML) {
           SanitizeAttributes(elt,
                              sAttributesHTML,
-                             (nsAtom***)kURLAttributesHTML,
+                             kURLAttributesHTML,
                              false,
                              mAllowStyles,
                              false);
         } else {
           SanitizeAttributes(elt,
                              sAttributesSVG,
-                             (nsAtom***)kURLAttributesSVG,
+                             kURLAttributesSVG,
                              true,
                              mAllowStyles,
                              false);
         }
         node = node->GetNextNonChildNode(aRoot);
         continue;
       }
       if (MustFlatten(ns, localName)) {
@@ -1462,31 +1462,31 @@ nsTreeSanitizer::SanitizeChildren(nsINod
       }
       NS_ASSERTION(ns == kNameSpaceID_XHTML ||
                    ns == kNameSpaceID_SVG ||
                    ns == kNameSpaceID_MathML,
           "Should have only HTML, MathML or SVG here!");
       if (ns == kNameSpaceID_XHTML) {
         SanitizeAttributes(elt,
                            sAttributesHTML,
-                           (nsAtom***)kURLAttributesHTML,
+                           kURLAttributesHTML,
                            false, mAllowStyles,
                            (nsGkAtoms::img == localName) &&
                            !mCidEmbedsOnly);
       } else if (ns == kNameSpaceID_SVG) {
         SanitizeAttributes(elt,
                            sAttributesSVG,
-                           (nsAtom***)kURLAttributesSVG,
+                           kURLAttributesSVG,
                            true,
                            mAllowStyles,
                            false);
       } else {
         SanitizeAttributes(elt,
                            sAttributesMathML,
-                           (nsAtom***)kURLAttributesMathML,
+                           kURLAttributesMathML,
                            true,
                            false,
                            false);
       }
       node = node->GetNextNode(aRoot);
       continue;
     }
     NS_ASSERTION(!node->GetFirstChild(), "How come non-element node had kids?");

--- a/dom/base/nsTreeSanitizer.h
+++ b/dom/base/nsTreeSanitizer.h
@@ -108,17 +108,17 @@ class MOZ_STACK_CLASS nsTreeSanitizer {
 
     /**
      * Checks if a given local name (for an attribute) is on the given list
      * of URL attribute names.
      * @param aURLs the list of URL attribute names
      * @param aLocalName the name to search on the list
      * @return true if aLocalName is on the aURLs list and false otherwise
      */
-    bool IsURL(nsAtom*** aURLs, nsAtom* aLocalName);
+    bool IsURL(nsAtom** const* aURLs, nsAtom* aLocalName);
 
     /**
      * Removes dangerous attributes from the element. If the style attribute
      * is allowed, its value is sanitized. The values of URL attributes are
      * sanitized, except src isn't sanitized when it is allowed to remain
      * potentially dangerous.
      *
      * @param aElement the element whose attributes should be sanitized
@@ -126,17 +126,17 @@ class MOZ_STACK_CLASS nsTreeSanitizer {
      * @param aURLs the local names of URL-valued attributes
      * @param aAllowXLink whether XLink attributes are allowed
      * @param aAllowStyle whether the style attribute is allowed
      * @param aAllowDangerousSrc whether to leave the value of the src
      *                           attribute unsanitized
      */
     void SanitizeAttributes(mozilla::dom::Element* aElement,
                             nsTHashtable<nsRefPtrHashKey<nsAtom>>* aAllowed,
-                            nsAtom*** aURLs,
+                            nsAtom** const* aURLs,
                             bool aAllowXLink,
                             bool aAllowStyle,
                             bool aAllowDangerousSrc);
 
     /**
      * Remove the named URL attribute from the element if the URL fails a
      * security check.
      *