This reintroduces bounds-checking for the CSS `<angle>`, `<frequency>`,
`<integer>`, `<length>`, `<number>`, `<percentage>`, `<resolution>`,
and `<time>` types.
I regressed this around 6b8f484114 when
changing how we parsed StyleValues.
This is an improvement from before though, since we now allow the bounds
of a dimension type to have units.
Added a test to make sure we don't regress this again. :^)
