Bug 1298243 part 2. Make the type of a DataTransferItem immutable. r=mystor

dom/events/DataTransferItem.cpp

@@ -73,12 +73,6 @@ DataTransferItem::Clone(DataTransfer* aDataTransfer) const
   return it.forget();
 }
 
-void
-DataTransferItem::SetType(const nsAString& aType)
-{
-  mType = aType;
-}
-
 void
 DataTransferItem::SetData(nsIVariant* aData)
 {

dom/events/DataTransferItem.h

@@ -73,7 +73,6 @@ public:
   {
     aType = mType;
   }
-  void SetType(const nsAString& aType);
 
   eKind Kind() const
   {
@@ -138,7 +137,7 @@ private:
 
   bool mChromeOnly;
   eKind mKind;
-  nsString mType;
+  const nsString mType;
   nsCOMPtr<nsIVariant> mData;
   nsCOMPtr<nsIPrincipal> mPrincipal;
   RefPtr<DataTransfer> mDataTransfer;