[touchable opacity] Set initial opacity based on style

[mlanter]

Set the initial opacity based on the style opacity instead of defaulting to 1. Without this change, if the opacity on the view is set to 0.5 (for example), the component will render with 1 opacity and then after a press and release it will set to 0.5. This fixes it to set to the correct value on mount.

Test plan (required)
Example code:

      <TouchableOpacity
        activeOpacity={1}
        style={STYLES.Button}>
        {...}
      </TouchableOpacity>

const STYLES = StyleSheet.create({
  Button: {
    opacity: 0.5,
  },
});

Before (notice starts out dark and then after click and release becomes light):

After (starts out light and is the same light color after a click and release):

[janicduplessis]

I know it was like this before but could you change this to == undefined so it also matches null.

[janicduplessis]

Thanks for the fix! Just one small change and we can ship this.

[eslint-bot]

eqeqeq: Expected '===' and instead saw '=='.

[janicduplessis]

@facebook-github-bot shipit

[facebook-github-bot]

@janicduplessis has imported this pull request. If you are a Facebook employee, you can view this diff on Phabricator.

[ryankask]

Should _opacityInactive() be called if the style prop's opacity is updated?

I have a several components that can be disabled and it would be nice to be able to fully control the inactive opacity using style.