Add ui::GrabDesktopSnapshot for Windows.

ui/snapshot/snapshot.gyp

Index: ui/snapshot/snapshot.gyp
diff --git a/ui/snapshot/snapshot.gyp b/ui/snapshot/snapshot.gyp
index 40744bfc768359129ecd467b2a9810dace3d3aeb..8712e01c106652a84b6026b900a09e6568870809 100644
--- a/ui/snapshot/snapshot.gyp
+++ b/ui/snapshot/snapshot.gyp
@@ -27,6 +27,7 @@
         'snapshot_ios.mm',
         'snapshot_mac.mm',
         'snapshot_win.cc',
+        'snapshot_win.h',
       ],
       'include_dirs': [
         '..',
@@ -38,11 +39,6 @@
             '../compositor/compositor.gyp:compositor',
           ],
         }],
-        ['use_aura==1 and OS=="win"', {
-          'sources/': [
-            ['exclude', 'snapshot_win.cc'],
-          ],
-        }],
       ],
     },
     {
@@ -62,4 +58,32 @@
       ]
     },
   ],
+  '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': [],
+        },
+      ],
+    }],
+  ],
 }