Perform "zoom compensation" for 'transform' on <svg:text>

SVGElement::calculateTransform would not compensate for effective zoom
on 'transform' for SVG <text> elements.
Refactor the code a bit so that the different parameter configurations
are selected first, and then use the same code for both <text> and non-
<text>. This makes sure that effective zoom is factored into the
computed transform for <text> as well.

BUG=665387,369942

Review-Url: https://codereview.chromium.org/2565403002
Cr-Commit-Position: refs/heads/master@{#437927}
3 files changed