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..927765a68ed0e74ef64fc98d6ee45c4b59c5a987 100644
--- a/ui/snapshot/snapshot.gyp
+++ b/ui/snapshot/snapshot.gyp
@@ -24,6 +24,8 @@
         'snapshot_aura.cc',
         'snapshot_export.h',
         'snapshot_gtk.cc',
+        'snapshot_hwnd_win.cc',

[sky, 2013/04/22 16:25:19]

Why is this file both here and in test support?

[grt (UTC plus 2), 2013/04/22 19:14:03]

The desktop snapshotting code (in 'snapshot_test_support' target) is identical
to the non-Aura window snapshotting code (in 'snapshot' target). To avoid source
code duplication, I pulled this implementation out of snapshot_win and into
snapshot_hwnd_win, and include it in both targets. It is omitted from 'snapshot'
for Aura builds, but is unconditionally present in 'snapshot_test_support' so
that desktop snapshotting can be done from tests. I experimented with having it
appear in only one or the other (and never both), but found that the gyp hijinks
to make that work was too confusing. I've moved desktop_snapshot.{cc,h} into a
test/ subdir to make it more explicit that these are test-only files.

+        'snapshot_hwnd_win.h',
         'snapshot_ios.mm',
         'snapshot_mac.mm',
         'snapshot_win.cc',
@@ -39,8 +41,10 @@
           ],
         }],
         ['use_aura==1 and OS=="win"', {
-          'sources/': [
-            ['exclude', 'snapshot_win.cc'],
+          'sources!': [
+            'snapshot_hwnd_win.cc',
+            'snapshot_hwnd_win.h',
+            'snapshot_win.cc',
           ],
         }],
       ],
@@ -62,4 +66,33 @@
       ]
     },
   ],
+  'conditions': [
+    ['OS=="win"', {
+      'targets': [
+        {
+          'target_name': 'snapshot_test_support',
+          'type': 'static_library',
+          'sources': [
+            'snapshot_desktop.h',
+            'snapshot_desktop_win.cc',
+            'snapshot_hwnd_win.cc',
+            'snapshot_hwnd_win.h',
+          ],
+          'dependencies': [
+            '../../base/base.gyp:base',
+            '../../skia/skia.gyp:skia',
+            '../ui.gyp:ui',
+          ],
+        },
+      ],
+    }, {  # else (OS!="win")
+      'targets': [
+        {
+          'target_name': 'snapshot_test_support',
+          'type': 'none',
+          'sources': [],
+        },
+      ],
+    }],
+  ],
 }