Remove screen capturers from media/video/capture/screen.

media/video/capture/screen/screen_capturer_null.cc

-// Copyright (c) 2013 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 "media/video/capture/screen/screen_capturer.h"
-
-namespace media {
-
-scoped_refptr<SharedBuffer> ScreenCapturer::Delegate::CreateSharedBuffer(
-    uint32 size) {
-  return scoped_refptr<SharedBuffer>();
-}
-
-void ScreenCapturer::Delegate::ReleaseSharedBuffer(
-    scoped_refptr<SharedBuffer> buffer) {
-}
-
-// static
-scoped_ptr<ScreenCapturer> ScreenCapturer::Create() {
-  return scoped_ptr<ScreenCapturer>();
-}
-
-// static
-scoped_ptr<ScreenCapturer> ScreenCapturer::CreateWithXDamage(
-    bool use_x_damage) {
-  return scoped_ptr<ScreenCapturer>();
-}
-
-}  // namespace media