Add NativePixmapHandle type & interface for exporting them

ui/ozone/platform/drm/gpu/gbm_buffer.h

 // Copyright 2014 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.
 
 #ifndef UI_OZONE_PLATFORM_DRM_GPU_GBM_BUFFER_H_
 #define UI_OZONE_PLATFORM_DRM_GPU_GBM_BUFFER_H_
 
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
 #include "ui/gfx/buffer_types.h"
@@ skipping 33 matching lines @@
 
   // NativePixmap:
   void* GetEGLClientBuffer() override;
   int GetDmaBufFd() override;
   int GetDmaBufPitch() override;
   bool ScheduleOverlayPlane(gfx::AcceleratedWidget widget,
                             int plane_z_order,
                             gfx::OverlayTransform plane_transform,
                             const gfx::Rect& display_bounds,
                             const gfx::RectF& crop_rect) override;
+  gfx::NativePixmapHandle ExportHandle() override;
 
   scoped_refptr<GbmBuffer> buffer() { return buffer_; }
 
  private:
   ~GbmPixmap() override;
   bool ShouldApplyScaling(const gfx::Rect& display_bounds,
                           const gfx::RectF& crop_rect,
                           gfx::Size* required_size);
 
   scoped_refptr<GbmBuffer> buffer_;
   int dma_buf_ = -1;
 
   ScreenManager* screen_manager_;  // Not owned.
 
   ScalingCallback scaling_callback_;
 
   DISALLOW_COPY_AND_ASSIGN(GbmPixmap);
 };
 
 }  // namespace ui
 
 #endif  // UI_OZONE_PLATFORM_DRM_GPU_GBM_BUFFER_H_