Blink, WebKit, and Gecko round the border-box geometry that feeds
offsetWidth and offsetHeight instead of truncating it. Do the same
in HTMLElement so these CSSOM View APIs match interop behavior for
fractional sizes.
This also updates the two local text expectations that changed
because they observe the rounded values.
When content changes inside a layout node, we now reset intrinsic size
caches only up to the nearest absolutely positioned ancestor, rather
than all the way to the document root.
This optimization is safe because absolutely positioned elements don't
contribute to their ancestors' intrinsic sizes - they are skipped in
min/max content width calculations.
The needs_layout_update flag still propagates to all ancestors so the
document knows layout is needed. Only the cache reset is bounded.
