Taskbar: Forgot to add WindowIdentifier.h.

Applications/Taskbar/WindowIdentifier.h

@@ -0,0 +1,32 @@
+#pragma once
+
+#include <AK/Traits.h>
+#include <AK/kstdio.h>
+
+class WindowIdentifier {
+public:
+    WindowIdentifier(int client_id, int window_id)
+        : m_client_id(client_id)
+        , m_window_id(window_id)
+    {
+    }
+
+    int client_id() const { return m_client_id; }
+    int window_id() const { return m_window_id; }
+
+    bool operator==(const WindowIdentifier& other) const
+    {
+        return m_client_id == other.m_client_id && m_window_id == other.m_window_id;
+    }
+private:
+    int m_client_id { -1 };
+    int m_window_id { -1 };
+};
+
+namespace AK {
+template<>
+struct Traits<WindowIdentifier> {
+    static unsigned hash(const WindowIdentifier& w) { return pair_int_hash(w.client_id(), w.window_id()); }
+    static void dump(const WindowIdentifier& w) { kprintf("WindowIdentifier(%d, %d)", w.client_id(), w.window_id()); }
+};
+}