Merge "[RenderEngine] correct alpha blending func" am: 6f94260396 am: 9592c9d586 am: d0567ad4a1 am: 444c983529 am: 228b500fe6

Original change: https://android-review.googlesource.com/c/platform/frameworks/native/+/1391116

Change-Id: I9ffe6ac0031d520f455e2f93260f78cd4e6a5a69