Add AshDesktopMediaList and enable Desktop Capture API on Chrome OS.

ui/snapshot/snapshot_android.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 "ui/snapshot/snapshot.h"
 
 #include "ui/base/android/view_android.h"
 #include "ui/base/android/window_android.h"
 #include "ui/gfx/display.h"
 #include "ui/gfx/rect.h"
@@ skipping 14 matching lines @@
   gfx::Display display =
       gfx::Screen::GetNativeScreen()->GetPrimaryDisplay();
   gfx::Rect scaled_bounds =
       gfx::ScaleToEnclosingRect(snapshot_bounds,
                                 display.device_scale_factor());
   return window->GrabSnapshot(
       scaled_bounds.x(), scaled_bounds.y(), scaled_bounds.width(),
       scaled_bounds.height(), png_representation);
 }
 
+SNAPSHOT_EXPORT void GrapWindowSnapshotAsync(
+    gfx::NativeWindow window,
+    const gfx::Rect& snapshot_bounds,
+    const gfx::Size& target_size,
+    scoped_refptr<base::TaskRunner> background_task_runner,
+    GrapWindowSnapshotAsyncCallback callback) {
+  NOTIMPLEMENTED();
+}
+
 }  // namespace ui