Bug 1678783 - Reuse linear filtering fast-paths for linear-repeat filtering. r=jrmuizel
Bug 1678783 - Reuse linear filtering fast-paths for linear-repeat filtering. r=jrmuizel

This reorganizes the blendTextureLinear code so that linear-repeat filtering
can reuse the linear filtering fast-paths. Otherwise, linear-repeat filtering
would previously only use the linear filtering fallback, when some patterns
like repeating background images are easily accelerated by these extra fast-paths.

Differential Revision: https://phabricator.services.mozilla.com/D110877

[ghsync] From https://hg.mozilla.org/mozilla-central/rev/dcc9ca0ad46eea95eacc9071ba55015a8803e224

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