inferred unused function names are not removed

[boopathi]

Describe the bug

Follow up of #842 -

Function names created by function name transformer of es2015 aren't removed when unused.

To Reproduce

Minimal code to reproduce the bug

function foo() {
  return {
    a() {}
  }
}

Actual Output

If there is no Error thrown,

function foo() {
  return {
    a: function b() {}
  };
}

Expected Output

function foo() {
  return {
    a: function() {}
  };
}

Configuration

babel-minify-cli

babel-minify version: master after #841

babel version : 7.0.0-beta.46

babel-minify-config:

{
  removeConsole: true,
  keepFnNames: true
}

babelrc:

{
  plugins: [],
  presets: []
}

Possible solution

Apply the same fix as in #842 - force register the binding (because this binding has been skipped by babel)