Update CSSTranslation.cssText to new style

[rjwright]

Make CSSTranslation.cssText reflect input text for parsed values & make it lazy.

Makes it consistent with https://github.com/css-typed-om/typed-om/pull/130/files (rotate and skew).

Other types will follow in separate PRs.

[wilddamon]

I really don't like this thing where we're modifying the private attributes of the result outside the css-translation.js file - this can get hard to reason about very quickly. What if instead we had internal-only functions internal.buildCSSTranslation(x, y, z) and internal.buildCSSTranslationX(x) etc, in css-translation.js, that attach the correct cssText method to the resulting object? I'm imagining something like this

function CSSTranslation(x, y, z) {...}
...
function buildCSSTranslationX(x) {
  var result = new CSSTranslation(x, zeroLength);
  Object.defineProperty(result, 'cssText', {
    get: function() { return cssTextX(this); },
    set: function(newText) {}
  });
  return result;
}

internal.buildCSSTranslationX = buildCSSTranslationX;

This also gets rid of the magic '1', '2', 'x' etc, which I also think is not so great.

[rjwright]

I think that might be more confusing, and add a lot of code. What about if we just set _cssText directly from the parser? That gets rid of the magic values.

[rjwright]

I think that might be more confusing, and add a lot of code. What about if we just set _cssText directly from the parser? That gets rid of the magic values.

Actually I can't completely get rid of the magic flags, but I won't have to store them. And I can put them in an enum.

[rjwright]

@wilddamon after talking to @shans and deciding we don't want to normalize cssText for parsed values, I have simplified the code and gotten rid of the magic flags.

I tried adding a factory for each input type, but I think was less readable. I also don't think we should move this logic into the class file, because it is a special case for parsing.

[rjwright]

I tried adding a factory for each input type, but I think was less readable. I also don't think we should move this logic into the class file, because it is a special case for parsing.

But then I did it anyway, cause I don't really mind :P

[wilddamon]

This wasn't what I was thinking either - now you've moved parsing logic into the main file. You can definitely keep them separate - I'll send you an example in a bit.