Extended error reporting for SVGNumber/Point/Rect and related types

Add extended error reporting for "number-based" types - SVGNumber,
SVGNumberList, SVGNumberOptionalNumber, SVGPoint, SVGPointList and
SVGRect.

Also clean up some of the parsing functions and eliminate some
unnecessary clear() calls in the list types.

BUG=231612

Review URL: https://codereview.chromium.org/1620203002

Cr-Commit-Position: refs/heads/master@{#371022}
14 files changed