Add GN files for ui/platform_window/win.

ui/platform_window/win/BUILD.gn

Index: ui/platform_window/win/BUILD.gn
diff --git a/ui/gfx/ipc/BUILD.gn b/ui/platform_window/win/BUILD.gn
similarity index 55%
copy from ui/gfx/ipc/BUILD.gn
copy to ui/platform_window/win/BUILD.gn
index b7b8efc5c0d127efa576b9efa6d6652a4941e8e0..26eb0aaadbf01f984eeb697ea94c902a3b6a1d38 100644
--- a/ui/gfx/ipc/BUILD.gn
+++ b/ui/platform_window/win/BUILD.gn
@@ -2,20 +2,21 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-component("ipc") {
-  output_name = "gfx_ipc"
-
-  sources = [
-    "gfx_param_traits.cc",
-    "gfx_param_traits.h",
-  ]
-
-  defines = [ "GFX_IPC_IMPLEMENTATION" ]
-
+component("win_window") {
   deps = [
     "//base",
-    "//ipc",
     "//skia",
+    "//ui/events",
+    "//ui/gfx",
     "//ui/gfx/geometry",
+    "//ui/platform_window",
+  ]
+
+  defines = [ "WIN_WINDOW_IMPLEMENTATION" ]
+
+  sources = [
+    "win_window.cc",
+    "win_window.h",
+    "win_window_export.h",
   ]
 }