Provide iOS implementation of screen.h.

ui/ui.gyp

 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 {
   'variables': {
     'chromium_code': 1,
   },
   'includes': [
     'ui_resources.gypi',
@@ skipping 35 matching lines @@
         'gfx/point.cc',
         'gfx/point.h',
         'gfx/point_base.h',
         'gfx/point3.h',
         'gfx/rect.cc',
         'gfx/rect.h',
         'gfx/rect_base.h',
         'gfx/rect_base_impl.h',
         'gfx/scoped_ui_graphics_push_context_ios.h',
         'gfx/scoped_ui_graphics_push_context_ios.mm',
+        'gfx/screen.h',
+        'gfx/screen_android.cc',
+        'gfx/screen_aura.cc',
+        'gfx/screen_gtk.cc',
+        'gfx/screen_impl.h',
+        'gfx/screen_ios.mm',
+        'gfx/screen_mac.mm',
+        'gfx/screen_win.cc',
         'gfx/size.cc',
         'gfx/size.h',
         'gfx/size_base.h',
         'gfx/size_base_impl.h',
       ],
       'all_sources': [
         '<@(_common_sources)',
         'base/accelerators/accelerator.cc',
         'base/accelerators/accelerator.h',
         'base/accelerators/accelerator_cocoa.h',
@@ skipping 368 matching lines @@
         'gfx/rect_f.cc',
         'gfx/rect_f.h',
         'gfx/render_text.cc',
         'gfx/render_text.h',
         'gfx/render_text_mac.cc',
         'gfx/render_text_mac.h',
         'gfx/render_text_linux.cc',
         'gfx/render_text_linux.h',
         'gfx/render_text_win.cc',
         'gfx/render_text_win.h',
-        'gfx/screen.h',
-        'gfx/screen_android.cc',
-        'gfx/screen_aura.cc',
-        'gfx/screen_gtk.cc',
-        'gfx/screen_impl.h',
-        'gfx/screen_mac.mm',
-        'gfx/screen_win.cc',
         'gfx/scoped_cg_context_save_gstate_mac.h',
         'gfx/scoped_ns_graphics_context_save_gstate_mac.h',
         'gfx/scoped_ns_graphics_context_save_gstate_mac.mm',
         'gfx/scrollbar_size.cc',
         'gfx/scrollbar_size.h',
         'gfx/selection_model.cc',
         'gfx/selection_model.h',
         'gfx/shadow_value.cc',
         'gfx/shadow_value.h',
         'gfx/size_f.cc',
@@ skipping 312 matching lines @@
     },
   ],
   'conditions': [
     ['inside_chromium_build == 1', {
       'includes': [
         'ui_unittests.gypi',
       ]},
     ],
   ],
 }