Bug 1593691 - Update comment about dual-source blending in text rendering doc. r=jrmuizel
Bug 1593691 - Update comment about dual-source blending in text rendering doc. r=jrmuizel

Differential Revision: https://phabricator.services.mozilla.com/D51622

[wrupdater] From https://hg.mozilla.org/mozilla-central/rev/4ad4fe8c0b482404e853f4206e46e42303d5830f

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