Make ChromeOS screenshots use async readback path

chrome/browser/ui/window_snapshot/window_snapshot.cc

 // 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.
 
 #include "chrome/browser/ui/window_snapshot/window_snapshot.h"
 
 #include "base/prefs/pref_registry_simple.h"
 #include "base/prefs/pref_service.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/common/pref_names.h"
 #include "ui/snapshot/snapshot.h"
 
 namespace chrome {
 
 bool GrabWindowSnapshotForUser(
     gfx::NativeWindow window,
     std::vector<unsigned char>* png_representation,
     const gfx::Rect& snapshot_bounds) {
   if (g_browser_process->local_state()->GetBoolean(prefs::kDisableScreenshots))
     return false;
   return ui::GrabWindowSnapshot(window, png_representation,
       snapshot_bounds);
 }
 
+void GrabWindowSnapshotForUserAsync(

[Jun Mukai, 2014/01/09 01:19:32]

I am not sure we need to declare this if the only user is ash/screenshot_taker.
Screenshot_taker already checks kDisableScreenshots, so you don't have to check
that again.

[enne (OOO), 2014/01/09 02:47:51]

That's a good point.  I'll remove this now and then come back and remove the
other sync version too once there's only caller in the future.

[enne (OOO), 2014/01/09 19:38:42]

Here's the followup to clean up window_snapshot once there's only one caller of
the sync version: https://codereview.chromium.org/132203004/

+    gfx::NativeWindow window,
+    const gfx::Rect& snapshot_bounds,
+    scoped_refptr<base::TaskRunner> background_task_runner,
+    ui::GrabWindowSnapshotAsyncPNGCallback callback) {
+  if (g_browser_process->local_state()->GetBoolean(prefs::kDisableScreenshots))
+    callback.Run(scoped_refptr<base::RefCountedBytes>());
+  ui::GrabWindowSnapshotAsync(
+      window, snapshot_bounds, background_task_runner, callback);
+}
+
 void RegisterScreenshotPrefs(PrefRegistrySimple* registry) {
   registry->RegisterBooleanPref(prefs::kDisableScreenshots, false);
 }
 
 }  // namespace chrome