Switch to new IOS windowing system.

This replaces the SDL-based system and should allow Metal to work on iOS.
OpenGL and raster will render but there's no touch input yet.

Bug: skia:8737
Change-Id: I863accc47f0e1781192d567dbe54d1e321c3cd2e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/231561
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Jim Van Verth <jvanverth@google.com>
diff --git a/BUILD.gn b/BUILD.gn
index 61baf01..cae7672 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -2375,11 +2375,12 @@
       ]
     } else if (is_ios) {
       sources += [
-        "tools/sk_app/ios/GLWindowContext_ios.cpp",
-        "tools/sk_app/ios/RasterWindowContext_ios.cpp",
-        "tools/sk_app/ios/Window_ios.cpp",
-        "tools/sk_app/ios/main_ios.cpp",
+        "tools/sk_app/ios/GLWindowContext_ios.mm",
+        "tools/sk_app/ios/RasterWindowContext_ios.mm",
+        "tools/sk_app/ios/Window_ios.mm",
+        "tools/sk_app/ios/main_ios.mm",
       ]
+      libs += [ "QuartzCore.framework" ]
     }
 
     if (skia_use_vulkan) {
@@ -2401,8 +2402,9 @@
       sources += [ "tools/sk_app/MetalWindowContext.mm" ]
       if (is_mac) {
         sources += [ "tools/sk_app/mac/MetalWindowContext_mac.mm" ]
+      } else if (is_ios) {
+        #        sources += [ "tools/sk_app/mac/MetalWindowContext_ios.mm" ]
       }
-      libs += [ "MetalKit.framework" ]
     }
 
     deps = [
@@ -2410,8 +2412,6 @@
     ]
     if (is_android) {
       deps += [ "//third_party/native_app_glue" ]
-    } else if (is_ios) {
-      deps += [ "//third_party/libsdl" ]
     }
     if (skia_use_angle) {
       deps += [ "//third_party/angle2" ]