Switch sk_app to use native window creation on MacOS.

Bug: skia:
Change-Id: I1763aab0b4bdb650128c1fcc3aa3a05d194496ca
Reviewed-on: https://skia-review.googlesource.com/c/186360
Commit-Queue: Jim Van Verth <jvanverth@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
diff --git a/BUILD.gn b/BUILD.gn
index 9d981b7..eb191dd 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -2124,10 +2124,10 @@
       }
     } else if (is_mac) {
       sources += [
-        "tools/sk_app/mac/GLWindowContext_mac.cpp",
-        "tools/sk_app/mac/RasterWindowContext_mac.cpp",
-        "tools/sk_app/mac/Window_mac.cpp",
-        "tools/sk_app/mac/main_mac.cpp",
+        "tools/sk_app/mac/GLWindowContext_mac.mm",
+        "tools/sk_app/mac/RasterWindowContext_mac.mm",
+        "tools/sk_app/mac/Window_mac.mm",
+        "tools/sk_app/mac/main_mac.mm",
       ]
       libs += [
         "QuartzCore.framework",
@@ -2162,7 +2162,7 @@
     ]
     if (is_android) {
       deps += [ "//third_party/native_app_glue" ]
-    } else if (is_mac || is_ios) {
+    } else if (is_ios) {
       deps += [ "//third_party/libsdl" ]
     }
     if (skia_use_angle) {