gl: Move platform-specific EGL code into separate files

ui/gl/gl_surface_osmesa.h

 // 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.
 
 #ifndef UI_GL_GL_SURFACE_OSMESA_H_
 #define UI_GL_GL_SURFACE_OSMESA_H_
 
 #include "base/memory/scoped_ptr.h"
 #include "ui/gfx/size.h"
 #include "ui/gl/gl_surface.h"
@@ skipping 21 matching lines @@
   virtual ~GLSurfaceOSMesa();
 
  private:
   unsigned format_;
   gfx::Size size_;
   scoped_ptr<int32[]> buffer_;
 
   DISALLOW_COPY_AND_ASSIGN(GLSurfaceOSMesa);
 };
 
+// A thin subclass of |GLSurfaceOSMesa| that can be used in place
+// of a native hardware-provided surface when a native surface
+// provider is not available.
+class GLSurfaceOSMesaHeadless : public GLSurfaceOSMesa {
+ public:
+  explicit GLSurfaceOSMesaHeadless();
+
+  virtual bool IsOffscreen() OVERRIDE;
+  virtual bool SwapBuffers() OVERRIDE;
+
+ protected:
+  virtual ~GLSurfaceOSMesaHeadless();
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(GLSurfaceOSMesaHeadless);
+};
+
 }  // namespace gfx
 
 #endif  // UI_GL_GL_SURFACE_OSMESA_H_