Vulkan: Add blend factors to allow dithering to work Previously, we had - src: GL_SRC_ALPHA, dst: GL_ONE_MINUS_SRC_ALPHA Now, this adds - src: GL_ONE, dst: GL_ONE_MINUS_SRC_ALPHA This showed up in app "com.inertiasoftware.justjigsaws". Bug: b/328837151 Change-Id: I88208b1ed4dd050283d8d02cf31ccdcb3d02a444 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/5369638 Commit-Queue: mohan maiya <m.maiya@samsung.com> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>