LibWeb: Add support for XMLHttpRequest request headers

Implement XMLHttpRequest.setRequestHeader() and include the headers in
the outgoing HTTP request.

Userland/Libraries/LibWeb/Bindings/XMLHttpRequestPrototype.cpp

@@ -43,6 +43,7 @@ void XMLHttpRequestPrototype::initialize(JS::GlobalObject& global_object)
     Object::initialize(global_object);
     define_native_function("open", open, 2);
     define_native_function("send", send, 0);
+    define_native_function("setRequestHeader", set_request_header, 2);
     define_native_property("readyState", ready_state_getter, nullptr, JS::Attribute::Enumerable | JS::Attribute::Configurable);
     define_native_property("responseText", response_text_getter, nullptr, JS::Attribute::Enumerable | JS::Attribute::Configurable);
 
@@ -93,6 +94,21 @@ JS_DEFINE_NATIVE_FUNCTION(XMLHttpRequestPrototype::send)
     return JS::js_undefined();
 }
 
+JS_DEFINE_NATIVE_FUNCTION(XMLHttpRequestPrototype::set_request_header)
+{
+    auto* impl = impl_from(vm, global_object);
+    if (!impl)
+        return {};
+    auto arg0 = vm.argument(0).to_string(global_object);
+    if (vm.exception())
+        return {};
+    auto arg1 = vm.argument(1).to_string(global_object);
+    if (vm.exception())
+        return {};
+    impl->set_request_header(arg0, arg1);
+    return JS::js_undefined();
+}
+
 JS_DEFINE_NATIVE_GETTER(XMLHttpRequestPrototype::ready_state_getter)
 {
     auto* impl = impl_from(vm, global_object);

Userland/Libraries/LibWeb/Bindings/XMLHttpRequestPrototype.h

@@ -41,6 +41,7 @@ public:
 private:
     JS_DECLARE_NATIVE_FUNCTION(open);
     JS_DECLARE_NATIVE_FUNCTION(send);
+    JS_DECLARE_NATIVE_FUNCTION(set_request_header);
 
     JS_DECLARE_NATIVE_GETTER(ready_state_getter);
     JS_DECLARE_NATIVE_GETTER(response_text_getter);

Userland/Libraries/LibWeb/DOM/XMLHttpRequest.cpp

@@ -63,10 +63,16 @@ String XMLHttpRequest::response_text() const
     return String::copy(m_response);
 }
 
+void XMLHttpRequest::set_request_header(const String& header, const String& value)
+{
+    m_request_headers.set(header, value);
+}
+
 void XMLHttpRequest::open(const String& method, const String& url)
 {
     m_method = method;
     m_url = url;
+    m_request_headers.clear();
     set_ready_state(ReadyState::Opened);
 }
 
@@ -88,10 +94,15 @@ void XMLHttpRequest::send()
         return;
     }
 
+    LoadRequest request;
+    request.set_url(m_window->document().complete_url(m_url));
+    for (auto& it : m_request_headers)
+        request.set_header(it.key, it.value);
+
     // FIXME: in order to properly set ReadyState::HeadersReceived and ReadyState::Loading,
     // we need to make ResourceLoader give us more detailed updates than just "done" and "error".
     ResourceLoader::the().load(
-        m_window->document().complete_url(m_url),
+        request,
         [weak_this = make_weak_ptr()](auto data, auto&) {
             if (!weak_this)
                 return;

Userland/Libraries/LibWeb/DOM/XMLHttpRequest.h

@@ -62,6 +62,8 @@ public:
     void open(const String& method, const String& url);
     void send();
 
+    void set_request_header(const String& header, const String& value);
+
 private:
     virtual void ref_event_target() override { ref(); }
     virtual void unref_event_target() override { unref(); }
@@ -79,6 +81,8 @@ private:
     String m_method;
     String m_url;
 
+    HashMap<String, String, CaseInsensitiveStringTraits> m_request_headers;
+
     ByteBuffer m_response;
 };