Fix for Preview has wrong location in MathML mode

The previewin MathML mode was always at the left side of the website.
Added values for `node.offsetWidth` and `node.offsetHeight`.
Values are taken from `node.getBoundingClientRect()`.
Cleaned up if-clause(node.dataset.title) as it is not needed anymore.
In-lined IsValidId funtion as there was only one remaining reference.

Bug: T381311
Change-Id: Ied17aaaaf9156e2712ed6c7d6d6f08ecccc12286
1 file changed
  NODES