Add Direct3D swapchain support

Change-Id: I4d4025fb842eb937785509bc7947f85f28a98ab8
Bug: skia:9935
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/288551
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Jim Van Verth <jvanverth@google.com>
diff --git a/BUILD.gn b/BUILD.gn
index 38f7e6e..aaa4e62 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -2193,6 +2193,10 @@
       }
     }
 
+    if (skia_use_direct3d) {
+      sources += [ "tools/sk_app/win/D3D12WindowContext_win.cpp" ]
+    }
+
     if (skia_use_dawn) {
       sources += [ "tools/sk_app/DawnWindowContext.cpp" ]
       if (is_linux) {