athena: Add a minimal executable for just the UI.

athena/ui/athena_ui_main.gyp

Index: athena/ui/athena_ui_main.gyp
diff --git a/athena/main/athena_main.gyp b/athena/ui/athena_ui_main.gyp
similarity index 54%
copy from athena/main/athena_main.gyp
copy to athena/ui/athena_ui_main.gyp
index 4a96c7753d3e5d6bc9a386a408a643fa9a818094..0daf9f1073afa247a83945b115a6b01b3aa9045a 100644
--- a/athena/main/athena_main.gyp
+++ b/athena/ui/athena_ui_main.gyp
@@ -8,22 +8,28 @@
   },
   'targets': [
     {
-      'target_name': 'athena_main',
+      'target_name': 'athena_ui_main',
       'type': 'executable',
       'dependencies': [
-        '../athena.gyp:athena_lib',
-        '../../apps/shell/app_shell.gyp:app_shell_lib',
+        '../../base/base.gyp:base',
+        '../../base/base.gyp:base_i18n',
         '../../skia/skia.gyp:skia',
         '../../ui/accessibility/accessibility.gyp:ax_gen',
+        '../../ui/aura/aura.gyp:aura',
+        '../../ui/aura/aura.gyp:aura_test_support',
+        '../../ui/compositor/compositor.gyp:compositor',
+        '../../ui/compositor/compositor.gyp:compositor_test_support',
+        '../../ui/gfx/gfx.gyp:gfx',
         '../../ui/views/views.gyp:views',
+        '../../ui/wm/wm.gyp:wm',
+        '../../ui/wm/wm.gyp:wm_test_support',
+        '../athena.gyp:athena_lib',
       ],
       'include_dirs': [
         '../..',
       ],
       'sources': [
-        'athena_main.cc',
-        'placeholder.cc',
-        'placeholder.h',
+        'athena_ui_main.cc',
       ],
     },
   ],  # targets