[Misc] (MG_Impl/Drawing): Test glClear in backend.

MobileGL/MG_Impl/GLImpl/Drawing/GL_Drawing.h

@@ -0,0 +1,10 @@
+#pragma once
+#include <Includes.h>
+
+namespace MobileGL {
+    namespace MG_Impl::GLImpl {
+        /* @INSERTION_POINT:FUNCTION_DECLARATION@ */
+        void Clear(GLbitfield mask);
+        void DrawElements(GLenum mode, GLsizei count, GLenum type, const void* indices);
+    } // namespace MG_Impl::GLImpl
+} // namespace MobileGL