Enable extension support and debug layer.

src/gpu/vk/GrVkUtil.h

Index: src/gpu/vk/GrVkUtil.h
diff --git a/src/gpu/vk/GrVkUtil.h b/src/gpu/vk/GrVkUtil.h
index 4fee31046d4560ce6ecac53b81388c255f5c0bff..0b760cabe2db1bcadc6514d548fe443581936668 100644
--- a/src/gpu/vk/GrVkUtil.h
+++ b/src/gpu/vk/GrVkUtil.h
@@ -14,6 +14,9 @@
 
 #include "vulkan/vulkan.h"
 
+// the minimum version of Vulkan supported
+const uint32_t kGrVkMinimumVersion = VK_MAKE_VERSION(1, 0, 3);
+
 // makes a Vk call on the interface
 #define GR_VK_CALL(IFACE, X) (IFACE)->fFunctions.f##X;
 // same as GR_VK_CALL but checks for success