ozone: gbm: Add overlay support

ui/ozone/platform/dri/gbm_buffer.h

Index: ui/ozone/platform/dri/gbm_buffer.h
diff --git a/ui/ozone/platform/dri/gbm_buffer.h b/ui/ozone/platform/dri/gbm_buffer.h
index a13fa356f8e8380fe37a165fb3d926943cdeff52..9f550ae9dfba94f29d6cb4410a745dfafbd1394d 100644
--- a/ui/ozone/platform/dri/gbm_buffer.h
+++ b/ui/ozone/platform/dri/gbm_buffer.h
@@ -8,6 +8,7 @@
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
 #include "ui/gfx/geometry/size.h"
+#include "ui/ozone/platform/dri/scanout_surface.h"
 #include "ui/ozone/public/native_pixmap.h"
 #include "ui/ozone/public/surface_factory_ozone.h"
 
@@ -18,7 +19,7 @@ namespace ui {
 
 class DriWrapper;
 
-class GbmBuffer : public NativePixmap {
+class GbmBuffer : public NativePixmap, public ScanoutSurface {
  public:
   GbmBuffer(gbm_device* device, DriWrapper* dri, const gfx::Size& size);
 
@@ -28,6 +29,14 @@ class GbmBuffer : public NativePixmap {
   virtual void* GetEGLClientBuffer() OVERRIDE;
   virtual int GetDmaBufFd() OVERRIDE;
 
+  // ScanoutSurface:
+  virtual bool Initialize() OVERRIDE;
+  virtual uint32_t GetFramebufferId() const OVERRIDE;
+  virtual uint32_t GetHandle() const OVERRIDE;
+  virtual gfx::Size Size() const OVERRIDE;
+  virtual void PreSwapBuffers() OVERRIDE;
+  virtual void SwapBuffers() OVERRIDE;
+
  protected:
   virtual ~GbmBuffer();