LibWeb: Begin implementing the WebDriver Input State and Input Source

These concepts are rather tightly coupled. This implements the types and
AOs needed to handle the Perform Actions endoint.

Userland/Libraries/LibWeb/WebDriver/InputState.cpp

@@ -0,0 +1,44 @@
+/*
+ * Copyright (c) 2024, Tim Flynn <trflynn89@ladybird.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibWeb/HTML/BrowsingContext.h>
+#include <LibWeb/WebDriver/Actions.h>
+#include <LibWeb/WebDriver/InputState.h>
+
+namespace Web::WebDriver {
+
+// https://w3c.github.io/webdriver/#dfn-browsing-context-input-state-map
+static HashMap<JS::RawGCPtr<HTML::BrowsingContext>, InputState> s_browsing_context_input_state_map;
+
+InputState::InputState() = default;
+InputState::~InputState() = default;
+
+// https://w3c.github.io/webdriver/#dfn-get-the-input-state
+InputState& get_input_state(HTML::BrowsingContext& browsing_context)
+{
+    // 1. Assert: browsing context is a top-level browsing context.
+    VERIFY(browsing_context.is_top_level());
+
+    // 2. Let input state map be session's browsing context input state map.
+    // 3. If input state map does not contain browsing context, set input state map[browsing context] to create an input state.
+    auto& input_state = s_browsing_context_input_state_map.ensure(browsing_context);
+
+    // 4. Return input state map[browsing context].
+    return input_state;
+}
+
+// https://w3c.github.io/webdriver/#dfn-reset-the-input-state
+void reset_input_state(HTML::BrowsingContext& browsing_context)
+{
+    // 1. Assert: browsing context is a top-level browsing context.
+    VERIFY(browsing_context.is_top_level());
+
+    // 2. Let input state map be session's browsing context input state map.
+    // 3. If input state map[browsing context] exists, then remove input state map[browsing context].
+    s_browsing_context_input_state_map.remove(browsing_context);
+}
+
+}