ZoneBinaryCallback bindBinaryCallback(dynamic f(arg1, arg2), {bool runGuarded: true})

Equivalent to:

 ZoneCallback registered = registerBinaryCallback(f);
 if (runGuarded) {
   return (arg1, arg2) => this.runBinaryGuarded(registered, arg);
 }
 return (arg1, arg2) => thin.runBinary(registered, arg1, arg2);

Source 

ZoneBinaryCallback/*<R, T1, T2>*/ bindBinaryCallback/*<R, T1, T2>*/(
    /*=R*/ f(/*=T1*/ arg1, /*=T2*/ arg2), { bool runGuarded: true });