Bug 1538540 - Respect texture_cache rebuild reqs even if doc has no pixels r=kvark
Bug 1538540 - Respect texture_cache rebuild reqs even if doc has no pixels r=kvark

If a document has an empty rect for whatever reason (in the case observed, this was
due to running a full screen video in the content document, which occludes the
chrome document), then we still want to ensure that we build a frame if the
texture cache has performed a clear, as otherwise we may try to access stale
items from the texture resolver in render_impl.

Differential Revision: https://phabricator.services.mozilla.com/D29848

[wrupdater] From https://hg.mozilla.org/mozilla-central/rev/ee580278f872fc2b68631da034d80a3dbf4eed2a

servo/webrender,servo/webrender,servo/webrender,servo/webrender,servo/webrender,servo/webrender