Set level count for wrapped backbuffer

tools/viewer/sk_app/VulkanWindowContext.cpp

Index: tools/viewer/sk_app/VulkanWindowContext.cpp
diff --git a/tools/viewer/sk_app/VulkanWindowContext.cpp b/tools/viewer/sk_app/VulkanWindowContext.cpp
index f21ec9c0cb5f74e282e28036dae07b737bef94d6..d2ea2bec4d98c401679a6467be0c68d4a89d61ae 100644
--- a/tools/viewer/sk_app/VulkanWindowContext.cpp
+++ b/tools/viewer/sk_app/VulkanWindowContext.cpp
@@ -261,6 +261,7 @@ void VulkanWindowContext::createBuffers(VkFormat format) {
         info.fImageLayout = VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL;
         info.fImageTiling = VK_IMAGE_TILING_OPTIMAL;
         info.fFormat = format;
+        info.fLevelCount = 1;
         desc.fWidth = fWidth;
         desc.fHeight = fHeight;
         desc.fConfig = fPixelConfig;