LibWeb: Save WebGL context pointer in WebGLObject

This way we could be sure that context object won't be deallocated
before any of the objects that belong to it.

Having a context pointer is also going to be used in upcoming changes
to generate an INVALID_OPERATION error if an object does not belong to
the context it's being used in.

Libraries/LibWeb/WebGL/WebGLRenderingContextBase.h

@@ -0,0 +1,18 @@
+/*
+ * Copyright (c) 2024, Aliaksandr Kalenik <kalenik.aliaksandr@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+namespace Web::WebGL {
+
+// FIXME: This object should inherit from Bindings::PlatformObject and implement the WebGLRenderingContextBase IDL interface.
+//        We should make WebGL code generator to produce implementation for this interface.
+class WebGLRenderingContextBase {
+public:
+    virtual GC::Cell const* gc_cell() const = 0;
+};
+
+}