LibWeb: Rename Origin::is_same() to Origin::is_same_origin()

The HTML Origin spec has two similar but slightly different concepts of
origin equality: "same origin" and "same origin-domain". Let's be
explicit with the naming here :^)
Also add spec comments.

Userland/Libraries/LibWeb/HTML/BrowsingContextContainer.cpp

@@ -48,7 +48,7 @@ bool BrowsingContextContainer::may_access_from_origin(const Origin& origin) cons
         if (!page->is_same_origin_policy_enabled())
             return true;
     }
-    return origin.is_same(content_origin());
+    return origin.is_same_origin(content_origin());
 }
 
 const DOM::Document* BrowsingContextContainer::content_document() const

Userland/Libraries/LibWeb/Origin.h

@@ -28,15 +28,22 @@ public:
     const String& host() const { return m_host; }
     u16 port() const { return m_port; }
 
-    bool is_same(const Origin& other) const
+    // https://html.spec.whatwg.org/multipage/origin.html#same-origin
+    bool is_same_origin(Origin const& other) const
     {
+        // 1. If A and B are the same opaque origin, then return true.
+        if (is_opaque() && other.is_opaque())
+            return true;
+
+        // 2. If A and B are both tuple origins and their schemes, hosts, and port are identical, then return true.
+        // 3. Return false.
         return protocol() == other.protocol()
             && host() == other.host()
             && port() == other.port();
     }
 
-    bool operator==(Origin const& other) const { return is_same(other); }
-    bool operator!=(Origin const& other) const { return !is_same(other); }
+    bool operator==(Origin const& other) const { return is_same_origin(other); }
+    bool operator!=(Origin const& other) const { return !is_same_origin(other); }
 
 private:
     String m_protocol;

Userland/Libraries/LibWeb/XHR/XMLHttpRequest.cpp

@@ -394,7 +394,7 @@ DOM::ExceptionOr<void> XMLHttpRequest::send(String body)
     if (auto* page = m_window->page())
         should_enforce_same_origin_policy = page->is_same_origin_policy_enabled();
 
-    if (should_enforce_same_origin_policy && !m_window->associated_document().origin().is_same(request_url_origin)) {
+    if (should_enforce_same_origin_policy && !m_window->associated_document().origin().is_same_origin(request_url_origin)) {
         dbgln("XHR failed to load: Same-Origin Policy violation: {} may not load {}", m_window->associated_document().url(), request_url);
         set_ready_state(ReadyState::Done);
         dispatch_event(DOM::Event::create(HTML::EventNames::error));