Align image sizes for SVG with raster image size

The background geometry calculations has heuristics for tiling image
sizes optimized for integer image sizes (at least in effective zoom ==
1). Rounding SVG image sizes before zoom application makes SVG images
fit better into the existing heuristics.

BUG=601011

Review URL: https://codereview.chromium.org/1912063004

Cr-Commit-Position: refs/heads/master@{#389158}
4 files changed