Add support for shared texture and external BeginFrame in OSR mode (issue #1006)

- Add CefWindowInfo::shared_texture_enabled and
  CefRenderHandler::OnAcceleratedPaint for shared texture support. Currently
  only supported on Windows (D3D11).
- Add CefWindowInfo::external_begin_frame_enabled and
  CefBrowserHost::SendExternalBeginFrame for external begin frame support.

libcef/browser/gpu/external_texture_manager.h

@@ -0,0 +1,46 @@
+// Copyright 2018 The Chromium Embedded Framework Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CEF_LIBCEF_BROWSER_GPU_EXTERNAL_TEXTURE_MANAGER_H_
+#define CEF_LIBCEF_BROWSER_GPU_EXTERNAL_TEXTURE_MANAGER_H_
+#pragma once
+
+#include <map>
+
+#include "gpu/command_buffer/service/texture_manager.h"
+#include "gpu/gpu_export.h"
+#include "ui/gl/gl_image.h"
+#include "ui/gl/gl_surface_egl.h"
+
+namespace gl {
+class GLImage;
+}
+
+namespace gpu {
+namespace gles2 {
+
+class GPU_GLES2_EXPORT ExternalTextureManager {
+ public:
+  ExternalTextureManager();
+  ~ExternalTextureManager();
+
+  void* CreateTexture(GLuint texture_id,
+                      uint32_t width,
+                      uint32_t height,
+                      TextureManager* tex_man);
+
+  void LockTexture(void* handle);
+  void UnlockTexture(void* handle);
+
+  void DeleteTexture(void* handle, TextureManager* tex_man);
+
+ private:
+  typedef std::map<void*, scoped_refptr<gl::GLImage>> ExternalSurfaceMap;
+  ExternalSurfaceMap surfaceMap_;
+};
+
+}  // namespace gles2
+}  // namespace gpu
+
+#endif  // CEF_LIBCEF_BROWSER_GPU_EXTERNAL_TEXTURE_MANAGER_H_