Windows: Add off-screen rendering support (issue #518).

- Popup menus, drag&drop and GPU acceleration are not currently supported.
- Testing is enabled in cefclient by passing the "off-screen-rendering-enabled" command-line flag.

git-svn-id: https://chromiumembedded.googlecode.com/svn/trunk@919 5089003a-bbd8-11dd-ad1f-f1f9622dbc98

libcef/browser/backing_store_osr.cc

@@ -0,0 +1,25 @@
+// 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 "libcef/browser/backing_store_osr.h"
+
+#include "ui/gfx/rect.h"
+
+BackingStoreOSR::BackingStoreOSR(content::RenderWidgetHost* widget,
+                                 const gfx::Size& size)
+    : content::BackingStore(widget, size) {
+  bitmap_.Allocate(size.width(), size.height(), true);
+}
+
+void BackingStoreOSR::ScrollBackingStore(const gfx::Vector2d& delta,
+                                         const gfx::Rect& clip_rect,
+                                         const gfx::Size& view_size) {
+  SkIRect subset_rect = SkIRect::MakeXYWH(clip_rect.x(), clip_rect.y(),
+      clip_rect.width(), clip_rect.height());
+  bitmap_.GetBitmap().scrollRect(&subset_rect, delta.x(), delta.y());
+}
+
+const void* BackingStoreOSR::getPixels() const {
+  return const_cast<BackingStoreOSR*>(this)->bitmap_.GetBitmap().getPixels();
+}