Change RenderObject::style(bool) to accept an enum instead

Change RenderObject::style(bool) to accept an enum instead

The rationale is that passing an enum is clearer in intent.

[davve, 2014-06-26 15:24:11]

Here's the POC of using a enum instead of style(bool). Take a look when you have
a moment.

I tried to reduce churn as much as possible by keeping variable names in the
cases where it made sense. In some cases the code got more readable (where
s/true/FirstLineStyle/) and in some cases a bit worse (when there are both a
bool and a OwnStyleOrFirstLineStyle on stack at the same time). I can try to
improve that if we find the overall direction to be good.

[esprehn, 2014-06-27 08:12:54]

This lgtm, the names are a little silly, but at least it's clear now. :)

[davve, 2014-06-30 10:13:40]

On 2014/06/27 08:12:54, esprehn wrote:
> This lgtm, the names are a little silly, but at least it's clear now. :)

Will continue on this after the fate of
https://codereview.chromium.org/358603002/ has been decided, since the two CLs
may conflict. Also, suggestions for non-silly names accepted :)

[davve, 2014-07-04 08:17:58]

I've now tried to decrease name silliness with one by renaming
OwnStyleOrFirstLineStyle to OwnOrFirstLineStyle. I also removed the double state
on the stack in RootInlineBox::verticalPositionForBox(). Still lots of code
churn for relatively little gain, so I'm not very confident about landing it.