Add COLOR_MODE_A8/ColorMode::A8

Currently unused. This will allow rending into A8 with HWUI

Bug: 193170859
Test: TODO
Change-Id: Ic1e1cb94dfa3dc08cbb174f0a38345d724570372
diff --git a/libs/hwui/pipeline/skia/SkiaPipeline.cpp b/libs/hwui/pipeline/skia/SkiaPipeline.cpp
index 4e7471d..bc386fe 100644
--- a/libs/hwui/pipeline/skia/SkiaPipeline.cpp
+++ b/libs/hwui/pipeline/skia/SkiaPipeline.cpp
@@ -613,6 +613,10 @@
             mSurfaceColorType = SkColorType::kRGBA_1010102_SkColorType;
             mSurfaceColorSpace = SkColorSpace::MakeRGB(GetPQSkTransferFunction(), SkNamedGamut::kRec2020);
             break;
+        case ColorMode::A8:
+            mSurfaceColorType = SkColorType::kAlpha_8_SkColorType;
+            mSurfaceColorSpace = nullptr;
+            break;
     }
 }