feat(OpenGL): Address rule CA1822

src/Avalonia.OpenGL/Controls/OpenGlControlBase.cs

@@ -27,7 +27,7 @@ namespace Avalonia.OpenGL.Controls
                 _context.GlInterface.BindFramebuffer(GL_FRAMEBUFFER, _fb);
                 EnsureTextureAttachment();
                 EnsureDepthBufferAttachment(_context.GlInterface);
-                if(!CheckFramebufferStatus(_context.GlInterface))
+                if(!OpenGlControlBase.CheckFramebufferStatus(_context.GlInterface))
                     return;
                 
                 OnOpenGlRender(_context.GlInterface, _fb);
@@ -38,7 +38,7 @@ namespace Avalonia.OpenGL.Controls
             base.Render(context);
         }
         
-        private void CheckError(GlInterface gl)
+        private static void CheckError(GlInterface gl)
         {
             int err;
             while ((err = gl.GetError()) != GL_NO_ERROR)
@@ -186,7 +186,7 @@ namespace Avalonia.OpenGL.Controls
                     EnsureDepthBufferAttachment(gl);
                     EnsureTextureAttachment();
 
-                    return CheckFramebufferStatus(gl);
+                    return OpenGlControlBase.CheckFramebufferStatus(gl);
                 }
                 catch(Exception e)
                 {
@@ -197,7 +197,7 @@ namespace Avalonia.OpenGL.Controls
             }
         }
 
-        private bool CheckFramebufferStatus(GlInterface gl)
+        private static bool CheckFramebufferStatus(GlInterface gl)
         {
             var status = gl.CheckFramebufferStatus(GL_FRAMEBUFFER);
             if (status != GL_FRAMEBUFFER_COMPLETE)