LibWeb: Implement a very basic WebAssembly JS API

This impl is *extremely* simple, and is missing a lot of things, it's
also not particularly spec-compliant in some places, but it's definitely
a start :^)

Userland/Libraries/LibWeb/WebAssembly/WebAssemblyObject.h

@@ -0,0 +1,96 @@
+/*
+ * Copyright (c) 2021, Ali Mohammad Pur <mpfard@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <LibJS/Runtime/Object.h>
+#include <LibWasm/AbstractMachine/AbstractMachine.h>
+#include <LibWeb/Forward.h>
+
+namespace Web::Bindings {
+
+class WebAssemblyObject final : public JS::Object {
+    JS_OBJECT(WebAssemblyObject, JS::Object);
+
+public:
+    explicit WebAssemblyObject(JS::GlobalObject&);
+    virtual void initialize(JS::GlobalObject&) override;
+    virtual ~WebAssemblyObject() override = default;
+
+    struct CompiledWebAssemblyModule {
+        explicit CompiledWebAssemblyModule(Wasm::Module&& module)
+            : module(move(module))
+        {
+        }
+
+        Wasm::Module module;
+    };
+
+    // FIXME: These should just be members of the module (instance) object,
+    //        but the module needs to stick around while its instance is alive
+    //        so ideally this would be a refcounted object, shared between
+    //        WebAssemblyModuleObject's and WebAssemblyInstantiatedModuleObject's.
+    static NonnullOwnPtrVector<CompiledWebAssemblyModule> s_compiled_modules;
+    static NonnullOwnPtrVector<Wasm::ModuleInstance> s_instantiated_modules;
+
+    static Wasm::AbstractMachine s_abstract_machine;
+
+private:
+    JS_DECLARE_NATIVE_FUNCTION(validate);
+    JS_DECLARE_NATIVE_FUNCTION(compile);
+    JS_DECLARE_NATIVE_FUNCTION(instantiate);
+};
+
+class WebAssemblyModuleObject final : public JS::Object {
+    JS_OBJECT(WebAssemblyModuleObject, JS::Object);
+
+public:
+    explicit WebAssemblyModuleObject(JS::GlobalObject&, size_t index);
+    virtual ~WebAssemblyModuleObject() override = default;
+
+    size_t index() const { return m_index; }
+    const Wasm::Module& module() const { return WebAssemblyObject::s_compiled_modules.at(m_index).module; }
+
+private:
+    size_t m_index { 0 };
+};
+
+class WebAssemblyInstancePrototype final : public JS::Object {
+    JS_OBJECT(WebAssemblyInstancePrototype, JS::Object);
+
+public:
+    explicit WebAssemblyInstancePrototype(JS::GlobalObject& global_object)
+        : JS::Object(global_object)
+    {
+    }
+
+    virtual void initialize(JS::GlobalObject&) override;
+
+private:
+    JS_DECLARE_NATIVE_GETTER(exports_getter);
+};
+
+class WebAssemblyInstanceObject final : public JS::Object {
+    JS_OBJECT(WebAssemblyInstanceObject, JS::Object);
+
+public:
+    explicit WebAssemblyInstanceObject(JS::GlobalObject&, size_t index);
+    virtual void initialize(JS::GlobalObject&) override;
+    virtual ~WebAssemblyInstanceObject() override = default;
+
+    size_t index() const { return m_index; }
+    Wasm::ModuleInstance& instance() const { return WebAssemblyObject::s_instantiated_modules.at(m_index); }
+
+    void visit_edges(Cell::Visitor&) override;
+
+    friend class WebAssemblyInstancePrototype;
+
+private:
+    size_t m_index { 0 };
+    JS::Object* m_exports_object { nullptr };
+};
+
+}