LibWeb: Add Origin::is_same(const Origin&)

Getting ready for some extremely basic same-origin policy stuff,
this initial implementation simply checks that two origins have
identical protocol, host and port.

Libraries/LibWeb/Origin.h

@@ -46,6 +46,13 @@ public:
     const String& host() const { return m_host; }
     u16 port() const { return m_port; }
 
+    bool is_same(const Origin& other) const
+    {
+        return protocol() == other.protocol()
+            && host() == other.host()
+            && port() == other.port();
+    }
+
 private:
     String m_protocol;
     String m_host;