Enable extension support and debug layer.

src/gpu/vk/GrVkGpu.h

Index: src/gpu/vk/GrVkGpu.h
diff --git a/src/gpu/vk/GrVkGpu.h b/src/gpu/vk/GrVkGpu.h
index 3785b15af10a23242d9721c9dc3096d81469dd03..c39973a4e786c2be20bcce10f98f5cb7a7083d4b 100644
--- a/src/gpu/vk/GrVkGpu.h
+++ b/src/gpu/vk/GrVkGpu.h
@@ -30,6 +30,10 @@ class GrVkRenderPass;
 class GrVkTexture;
 struct GrVkInterface;
 
+#ifdef SK_DEBUG
+#define ENABLE_VK_LAYERS
+#endif
+
 class GrVkGpu : public GrGpu {
 public:
     // Currently passing in the inst so that we can properly delete it when we are done.
@@ -218,6 +222,11 @@ private:
     GrVkCommandBuffer*                fCurrentCmdBuffer;
     GrVkResourceProvider              fResourceProvider;
 
+#ifdef ENABLE_VK_LAYERS
+    // For reporting validation layer errors
+    VkDebugReportCallbackEXT          fCallback;
+#endif
+
     // Shaderc compiler used for compiling glsl in spirv. We only want to create the compiler once
     // since there is significant overhead to the first compile of any compiler.
     shaderc_compiler_t fCompiler;