Support fragment URLs for more kinds of SVG images

This patch adds support for SVG fragment URLs in CSS backgrounds,
video poster images, image inputs, content property and svg:image
scenarios. It does so by storing fragment URLs for each
SVGImageForContainer and propgates this URL to SVGImage when drawing.

BUG=128055

Review URL: https://codereview.chromium.org/1458083002

Cr-Commit-Position: refs/heads/master@{#360787}
25 files changed