Replace ShapeValue::IsImageValid with StyleImage::CanRender

The former looks like an open-coded version of the latter. Using the
latter will be more consistent (and future-safe.)

Change-Id: I3353d0181201df681779575d78fe0df22065a9e4
Reviewed-on: https://chromium-review.googlesource.com/c/1280447
Reviewed-by: Stephen Chenney <schenney@chromium.org>
Commit-Queue: Fredrik Söderquist <fs@opera.com>
Cr-Commit-Position: refs/heads/master@{#599691}
4 files changed