Support GL_RGB textures and render targets.

Bug= skia:7533

Change-Id: Iba30e90dbf2574368b773bb5cf2ebd5219559717
Reviewed-on: https://skia-review.googlesource.com/108188
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
diff --git a/src/gpu/vk/GrVkUtil.cpp b/src/gpu/vk/GrVkUtil.cpp
index 4f0acdb..e61d7bc 100644
--- a/src/gpu/vk/GrVkUtil.cpp
+++ b/src/gpu/vk/GrVkUtil.cpp
@@ -22,6 +22,9 @@
         case kRGBA_8888_GrPixelConfig:
             *format = VK_FORMAT_R8G8B8A8_UNORM;
             return true;
+        case kRGB_888_GrPixelConfig:
+            // TODO: VK_FORMAT_R8G8B8_UNORM
+            return false;
         case kBGRA_8888_GrPixelConfig:
             *format = VK_FORMAT_B8G8R8A8_UNORM;
             return true;