Remove openglui embedder code

runtime/embedders/openglui/common/isized.h

-// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-#ifndef EMBEDDERS_OPENGLUI_COMMON_ISIZED_H_
-#define EMBEDDERS_OPENGLUI_COMMON_ISIZED_H_
-
-#include <stdint.h>
-
-// An interface for objects that have a size. VMGlue needs the window
-// size when calling setup() (and eventually resize()) but it does not
-// need to know anything else about the window, so we use this interface.
-class ISized {
-  public:
-    virtual const int32_t& height() = 0;
-    virtual const int32_t& width() = 0;
-    virtual ~ISized() {}
-};
-
-#endif  // EMBEDDERS_OPENGLUI_COMMON_ISIZED_H_
-