Uninline unit-accessors in LayoutSVGResource{Clipper,Masker}

This uninlines MaskUnits() and MaskContentUnits() in
LayoutSVGResourceMasker as well as ClipPathUnits() in
LayoutSVGResourceClipper - reducing unnecessary includes/dependencies.
Also streamline LayoutSVGResourceFilter::ResourceBoundingBox a bit by
using the FilterUnits() accessor, and remove the redundant null-check on
the element.

Change-Id: I658b7626627ac38fc8b43bfd54630adb778233e8
Reviewed-on: https://chromium-review.googlesource.com/1243117
Reviewed-by: Stephen Chenney <schenney@chromium.org>
Commit-Queue: Fredrik Söderquist <fs@opera.com>
Cr-Commit-Position: refs/heads/master@{#594040}
6 files changed