diff --git a/mozilla/layout/style/nsCSSValue.h b/mozilla/layout/style/nsCSSValue.h
index 8179bec72e6..2a55d3b5003 100644
--- a/mozilla/layout/style/nsCSSValue.h
+++ b/mozilla/layout/style/nsCSSValue.h
@@ -305,9 +305,9 @@ public:
     nsCSSValue& Item(PRUint16 aIndex) { return (*this)[aIndex]; }
     const nsCSSValue& Item(PRUint16 aIndex) const { return (*this)[aIndex]; }
 
-    PRUint16 Count() { return mCount; }
+    PRUint16 Count() const { return mCount; }
 
-    PRBool operator==(const Array& aOther)
+    PRBool operator==(const Array& aOther) const
     {
       if (mCount != aOther.mCount)
         return PR_FALSE;
@@ -393,7 +393,7 @@ public:
       MOZ_COUNT_DTOR(nsCSSValue::URL);
     }
 
-    PRBool operator==(const URL& aOther)
+    PRBool operator==(const URL& aOther) const
     {
       PRBool eq;
       return NS_strcmp(GetBufferValue(mString),
diff --git a/mozilla/layout/style/nsStyleStruct.cpp b/mozilla/layout/style/nsStyleStruct.cpp
index b71b252ab41..e3c18aebc14 100644
--- a/mozilla/layout/style/nsStyleStruct.cpp
+++ b/mozilla/layout/style/nsStyleStruct.cpp
@@ -1271,7 +1271,7 @@ nsStyleContentData& nsStyleContentData::operator=(const nsStyleContentData& aOth
   return *this;
 }
 
-PRBool nsStyleContentData::operator==(const nsStyleContentData& aOther)
+PRBool nsStyleContentData::operator==(const nsStyleContentData& aOther) const
 {
   if (mType != aOther.mType)
     return PR_FALSE;
diff --git a/mozilla/layout/style/nsStyleStruct.h b/mozilla/layout/style/nsStyleStruct.h
index ecb0456cce4..dfcd0cd0731 100644
--- a/mozilla/layout/style/nsStyleStruct.h
+++ b/mozilla/layout/style/nsStyleStruct.h
@@ -918,9 +918,9 @@ struct nsStyleContentData {
   nsStyleContentData() : mType(nsStyleContentType(0)) { mContent.mString = nsnull; }
   ~nsStyleContentData();
   nsStyleContentData& operator=(const nsStyleContentData& aOther);
-  PRBool operator==(const nsStyleContentData& aOther);
+  PRBool operator==(const nsStyleContentData& aOther) const;
 
-  PRBool operator!=(const nsStyleContentData& aOther) {
+  PRBool operator!=(const nsStyleContentData& aOther) const {
     return !(*this == aOther);
   }
 private: