Add Quick View image load test

Now we have the QuickView <webview> infra to detect the 'loaded' state
of thew <webview> content, add a <file-safe-media> image test and also
check the <webview> renders its content on a transparent black body.

Bug: 891150
Change-Id: I8e6aac85ce09e0fcbe0cbba660630d1427e2962b
Reviewed-on: https://chromium-review.googlesource.com/c/1263678
Reviewed-by: Luciano Pacheco <lucmult@chromium.org>
Commit-Queue: Noel Gordon <noel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#596989}
1 file changed