GL: Emulate SRGB blits where needed. Desktop OpenGL before 4.4 doesn't handle SRGB blits the same way OpenGL ES does. Emulate them by drawing a quad. BUG=angleproject:1492 BUG=chromium:634525 Change-Id: I9f2992d9b373941b10f19f8a51564f0f756cc4df Reviewed-on: https://chromium-review.googlesource.com/389853 Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Corentin Wallez <cwallez@chromium.org>