Bug 1257389: Use fallible allocation for content-controlled string in bug 1257389. r=bz

--HG--
extra : rebase_source : 904526e9c7ef9a90ac0bb73984af5d95dd8e60fc

dom/bindings/BindingUtils.cpp

@@ -2452,7 +2452,10 @@ ConvertJSValueToByteString(JSContext* cx, JS::Handle<JS::Value> v,
   static_assert(js::MaxStringLength < UINT32_MAX,
                 "length+1 shouldn't overflow");
 
-  result.SetLength(length);
+  if (!result.SetLength(length, fallible)) {
+    return false;
+  }
+
   JS_EncodeStringToBuffer(cx, s, result.BeginWriting(), length);
 
   return true;