Add Xlib support to viewer

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 bc200de42704a57ece5760bf082b1bbdf5490a02..2e2b8a988c01205f23d1e9bc6c64b93dd4d8ebc8 100644
--- a/tools/viewer/sk_app/VulkanWindowContext.cpp
+++ b/tools/viewer/sk_app/VulkanWindowContext.cpp
@@ -41,8 +41,9 @@ VulkanWindowContext::VulkanWindowContext(void* platformData, const DisplayParams
 }
 
 void VulkanWindowContext::initializeContext(void* platformData, const DisplayParams& params) {
+    fBackendContext.reset(GrVkBackendContext::Create(&fPresentQueueIndex, canPresent, 
+                                                     platformData));
 
-    fBackendContext.reset(GrVkBackendContext::Create(&fPresentQueueIndex, canPresent));
     if (!(fBackendContext->fExtensions & kKHR_surface_GrVkExtensionFlag) ||
         !(fBackendContext->fExtensions & kKHR_swapchain_GrVkExtensionFlag)) {
         fBackendContext.reset(nullptr);
@@ -147,6 +148,7 @@ bool VulkanWindowContext::createSwapchain(uint32_t width, uint32_t height,
     } else if (extent.height > caps.maxImageExtent.height) {
         extent.height = caps.maxImageExtent.height;
     }
+
     fWidth = (int)extent.width;
     fHeight = (int)extent.height;