[SkSVGDevice] Fix whitespace text handling

SVG ignores leading/trailing whitespace and consolidates mid-text
(http://www.w3.org/TR/SVG/text.html#WhiteSpace). This can cause our
x/y position indices to get out of whack.

Implement a text builder which is SVG whitespace-munging-aware and
performs the needed x/y position list adjustments.

R=reed@google.com,mtklein@google.com

Review URL: https://codereview.chromium.org/928583003
1 file changed