Added PlatformHandle thunks.

mojo/public/platform/native/BUILD.gn

Index: mojo/public/platform/native/BUILD.gn
diff --git a/mojo/public/platform/native/BUILD.gn b/mojo/public/platform/native/BUILD.gn
index e9c60343f315d438e5d453d95dda9f11ec540c7f..e88ac01612e236cf9f0e3785be1550039970bc18 100644
--- a/mojo/public/platform/native/BUILD.gn
+++ b/mojo/public/platform/native/BUILD.gn
@@ -3,6 +3,7 @@
 # found in the LICENSE file.
 
 import("../../mojo_sdk.gni")
+import("../../mojo_application.gni")
 
 mojo_sdk_source_set("system") {
   sources = [
@@ -125,3 +126,51 @@ mojo_sdk_source_set("mgl_onscreen_thunks") {
 
   mojo_sdk_deps = [ "mojo/public/c/gpu:MGL_onscreen" ]
 }
+
+mojo_sdk_source_set("platform_handle") {
+  sources = [
+    "platform_handle_private_thunks.c",
+    "platform_handle_private_thunks.h",
+  ]
+
+  mojo_sdk_deps = [
+    "mojo/public/platform/native:platform_handle_api",
+    "mojo/public/c/system",
+  ]
+}
+
+# Only targets that are calling the thunks should depend upon this.
+mojo_sdk_source_set("platform_handle_api") {
+  sources = [
+    "platform_handle_private.h",
+  ]
+  mojo_sdk_deps = [ "mojo/public/c/system:system" ]
+}
+
+mojo_native_application("platform_handle_private_apptest") {
+  output_name = "platform_handle_private_apptests"
+
+  testonly = true
+
+  sources = [
+    "platform_handle_private_apptest.cc",
+  ]
+
+  deps = [
+    ":platform_handle",
+    ":platform_handle_api",
+    "../../cpp/application:standalone",
+    "../../cpp/application:test_support_standalone",
+    "../../cpp/environment",
+    "../../cpp/system",
+  ]
+}
+
+group("tests") {
+  testonly = true
+
+  deps = [
+    ":platform_handle_private_apptest",
+    ":system_impl_private_tests",
+  ]
+}