Add ui::GrabDesktopSnapshot for Windows.

ui/snapshot/snapshot.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,
   },
   'targets': [
     {
       'target_name': 'snapshot',
       'type': '<(component)',
       'dependencies': [
         '../../skia/skia.gyp:skia',
         '../../base/base.gyp:base',
         '../ui.gyp:ui',
       ],
       'defines': [
         'SNAPSHOT_IMPLEMENTATION',
       ],
       'sources': [
         'snapshot.h',
         'snapshot_android.cc',
         'snapshot_aura.cc',
         'snapshot_export.h',
         'snapshot_gtk.cc',
         'snapshot_ios.mm',
         'snapshot_mac.mm',
         'snapshot_win.cc',
+        'snapshot_win.h',
       ],
       'include_dirs': [
         '..',
       ],
       'conditions': [
         ['use_aura==1', {
           'dependencies': [
             '../aura/aura.gyp:aura',
             '../compositor/compositor.gyp:compositor',
           ],
         }],
-        ['use_aura==1 and OS=="win"', {
-          'sources/': [
-            ['exclude', 'snapshot_win.cc'],
-          ],
-        }],
       ],
     },
     {
       'target_name': 'snapshot_unittests',
       'type': '<(gtest_target_type)',
       'dependencies': [
         '../../skia/skia.gyp:skia',
         '../../base/base.gyp:base',
         '../../testing/gtest.gyp:gtest',
         '../../testing/gmock.gyp:gmock',
         '../../testing/gtest.gyp:gtest',
         '../ui.gyp:ui',
         'snapshot'
       ],
       'sources': [
         'snapshot_mac_unittest.mm',
       ]
     },
   ],
+  'conditions': [
+    ['OS=="win"', {
+      'targets': [
+        {
+          'target_name': 'snapshot_test_support',
+          'type': 'static_library',
+          'sources': [
+            'test/snapshot_desktop.h',
+            'test/snapshot_desktop_win.cc',
+          ],
+          'dependencies': [
+            'snapshot'
+          ],
+          'include_dirs': [
+            '../..',
+          ],
+        },
+      ],
+    }, {  # else (OS!="win")
+      'targets': [

[sky, 2013/04/24 14:49:11]

Shouldn't we only include this target on windows so that you don't need to
create an empty target here?

[grt (UTC plus 2), 2013/04/24 17:44:47]

There's only the Windows implementation for now, but that could change if
someone became motivated to take care of other platforms. I figured it was
easier to have one win-only condition here (with the empty target for non-win
platforms) rather than one per use of the target in other .gyp* files. There's
only one use of it at the moment, so it's not a big deal either way. I suppose
the empty target could add a little overhead to non-Win platforms, so I've
removed it.

+        {
+          'target_name': 'snapshot_test_support',
+          'type': 'none',
+          'sources': [],
+        },
+      ],
+    }],
+  ],
 }