Update the sk_app WindowContext to hold a GrDirectContext

This CL is working towards replacing GrContext with the GrDirectContext/
GrRecordingContext pair.

Change-Id: Id4488e1280d76a16c37d58bd8d29fb7f8dde6b1d
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/301940
Reviewed-by: Adlai Holler <adlai@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
diff --git a/BUILD.gn b/BUILD.gn
index af01fd2..af9134b 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -2247,6 +2247,7 @@
       "tools/sk_app/RasterWindowContext.h",
       "tools/sk_app/Window.cpp",
       "tools/sk_app/Window.h",
+      "tools/sk_app/WindowContext.cpp",
       "tools/sk_app/WindowContext.h",
     ]
     libs = []