Use Windowing system-specific WindowContext factories.

tools/viewer/sk_app/unix/Window_unix.cpp

Index: tools/viewer/sk_app/unix/Window_unix.cpp
diff --git a/tools/viewer/sk_app/unix/Window_unix.cpp b/tools/viewer/sk_app/unix/Window_unix.cpp
index c4729263eca9a144cc1419e815d45ebb5c0b6f3b..e6edfd9ef9b0cbcde91f2e2db7fd317f286d9b41 100644
--- a/tools/viewer/sk_app/unix/Window_unix.cpp
+++ b/tools/viewer/sk_app/unix/Window_unix.cpp
@@ -7,12 +7,11 @@
 
 //#include <tchar.h>
 
+#include "WindowContextFactory_unix.h"
+
 #include "SkUtils.h"
 #include "Timer.h"
 #include "../GLWindowContext.h"
-#ifdef SK_VULKAN
-#include "../VulkanWindowContext.h"
-#endif
 #include "Window_unix.h"
 
 extern "C" {
@@ -273,19 +272,19 @@ void Window_unix::show() {
 bool Window_unix::attach(BackendType attachType, const DisplayParams& params) {
     this->initWindow(fDisplay, &params);
 
-    ContextPlatformData_unix platformData;
-    platformData.fDisplay = fDisplay;
-    platformData.fWindow = fWindow;
-    platformData.fVisualInfo = fVisualInfo;
+    window_context_factory::XlibWindowInfo xwinInfo;
+    xwinInfo.fDisplay = fDisplay;
+    xwinInfo.fWindow = fWindow;
+    xwinInfo.fVisualInfo = fVisualInfo;
     switch (attachType) {
 #ifdef SK_VULKAN
         case kVulkan_BackendType:
-            fWindowContext = VulkanWindowContext::Create((void*)&platformData, params);
+            fWindowContext = window_context_factory::NewVulkanForXlib(xwinInfo, params);
             break;
 #endif
         case kNativeGL_BackendType:
         default:
-            fWindowContext = GLWindowContext::Create((void*)&platformData, params);
+            fWindowContext = window_context_factory::NewGLForXlib(xwinInfo, params);
             break;
     }