gl: Move platform-specific EGL code into separate files

ui/gl/gl_surface_osmesa.h

Index: ui/gl/gl_surface_osmesa.h
diff --git a/ui/gl/gl_surface_osmesa.h b/ui/gl/gl_surface_osmesa.h
index a823231fa0c44eccbe29e0ae3d114dd5e4cd64ab..b4b48274913e2848c991b004c04fce808bde4c9d 100644
--- a/ui/gl/gl_surface_osmesa.h
+++ b/ui/gl/gl_surface_osmesa.h
@@ -39,6 +39,23 @@ class GL_EXPORT GLSurfaceOSMesa : public GLSurface {
   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_