Resolve percentage in <use> against the instance's viewport element
In LayoutSVGTransformableContainer::calculateLocalTransform, 'x' and 'y'
were resolved against the original (corresponding) element. For a <use>
nested within a <symbol>, this would mean that when were going to look
up the viewport element, we'd return the outer <symbol> element and thus
fail to get a viewport.
Use the instance element to setup the SVGLengthContext instead.
BUG=642524
Review-Url: https://codereview.chromium.org/2298783002
Cr-Commit-Position: refs/heads/master@{#415910}
3 files changed
