Compilation of WebKitGTK/WPE in ARM64 is failing with the following build error:

```
FAILED: Source/WebCore/CMakeFiles/WebCore.dir/platform/graphics/opengl/GraphicsContextGLOpenGLES.cpp.o
<CXX>  -DBUILDING_GTK__=1 -DBUILDING_WEBKIT=1 -DBUILDING_WITH_CMAKE=1 -DBUILDING_WebCore -DGETTEXT_PACKAGE=\"WebKitGTK-4.0\" -DHAVE_CONFIG_H=1 -DJSC_GLIB_API_ENABLED -DPAS_BMALLOC=1 -DSTATICALLY_LINKED_WITH_PAL -ISource/ThirdParty/libwebrtc -I../../../Source/WebCore/platform/graphics/libwpe -I. -IWebCore/DerivedSources -I../../..
../../../Source/WebCore/platform/graphics/opengl/GraphicsContextGLOpenGLES.cpp:61:60: error: reference to non-static member function must be called; did you mean to call it with no arguments?
    ::glReadPixels(x, y, width, height, format, type, data.data);
                                                      ~~~~~^~~~
                                                               ()
../../../Source/WebCore/platform/graphics/opengl/GraphicsContextGLOpenGLES.cpp:217:34: error: reference to non-static member function must be called; did you mean to call it with no arguments?
    ::glGetIntegerv(pname, value.data);
                           ~~~~~~^~~~
                                     ()
../../../Source/WebCore/platform/graphics/opengl/GraphicsContextGLOpenGLES.cpp:228:67: error: reference to non-static member function must be called; did you mean to call it with no arguments?
    ::glGetShaderPrecisionFormat(shaderType, precisionType, range.data, precision);
                                                            ~~~~~~^~~~
                                                                      ()
../../../Source/WebCore/platform/graphics/opengl/GraphicsContextGLOpenGLES.cpp:233:36: error: reference to non-static member function must be called; did you mean to call it with no arguments?
    if (width && height && !pixels.data) {
                            ~~~~~~~^~~~
                                       ()
../../../Source/WebCore/platform/graphics/opengl/GraphicsContextGLOpenGLES.cpp:238:97: error: reference to non-static member function must be called; did you mean to call it with no arguments?
    texImage2DDirect(target, level, internalformat, width, height, border, format, type, pixels.data);
                                                                                         ~~~~~~~^~~~
                                                                                                    ()
5 errors generated.
```

This build error was likely introduced in 254207@main, which turned `GCGLSpan::data` attribute into member function `GCGLSpan::data()`.