Function name shortened, but not function call

There seems to be a problem with shortening names in some cases. Below is an example.

```js
{
addOnclick: function(){
element.onclick = ()=>{this.foo("some string")};
},

foo: function(str){
//do things
}
}
```

I get: "this.foo is not a function"
What it looks like is happening is that it is changing the name of the function, but it is not changing the call to that function. It seems to do this everywhere that I have this format as far as I can tell. It works with browserify of course, but it breaks with tinyify.

Issue の JavaScript の例から始めて、tinyify を通して再現し、出力を browserify と比較します。名前短縮の経路を追跡し、短縮された関数名とその呼び出しが一貫して変更されることを確認します。完了の条件は、その例で "this.foo is not a function" が発生しなくなることです。

索引モデルが issue の本文から書いたものです。