[css-cascade] Make it clearer exactly what origins are being compared for @import in a quirks-mode document. Fixes #4838.

Author: tabatkins

css-cascade-4/Overview.bs

@@ -228,12 +228,15 @@ Processing Stylesheet Imports</h3>
 <h3 id='content-type'>
 Content-Type of CSS Style Sheets</h3>
 
-	The processing of imported style sheets depends on the actual type of the linked resource.
-	If the resource does not have <a href="https://html.spec.whatwg.org/multipage/urls-and-fetching.html#content-type">Content-Type metadata</a>,
-	or the host document is in <a href="https://html.spec.whatwg.org/multipage/infrastructure.html#quirks-mode">quirks mode</a>
-	and has the <a href="https://html.spec.whatwg.org/multipage/origin.html#same-origin">same origin</a> as the imported style sheet,
-	the type of the linked resource is <code>text/css</code>.
-	Otherwise, the type is determined from its <a href="https://html.spec.whatwg.org/multipage/urls-and-fetching.html#content-type">Content-Type metadata</a>.
+	The processing of imported style sheets depends on the actual type of the linked resource:
+
+	* If the resource does not have <l spec=html>[=Content-Type metadata=]</l>,
+		the type is treated as <code>text/css</code>.
+	* If the host document is in [=quirks mode=],
+		and the host document's origin is [=same origin=]
+		with the linked resource [=/response's=] [=response/URL's=] origin,
+		the type is treated as <code>text/css</code>.
+	* Otherwise, the type is determined from its <l spec=html>[=Content-Type metadata=]</l>.
 
 	If the linked resource's type is <code>text/css</code>,
 	it must be interpreted as a CSS style sheet.

css-cascade-5/Overview.bs

@@ -221,12 +221,15 @@ Processing Stylesheet Imports</h3>
 <h3 id='content-type'>
 Content-Type of CSS Style Sheets</h3>
 
-	The processing of imported style sheets depends on the actual type of the linked resource.
-	If the resource does not have <a href="https://html.spec.whatwg.org/multipage/urls-and-fetching.html#content-type">Content-Type metadata</a>,
-	or the host document is in <a href="https://html.spec.whatwg.org/multipage/infrastructure.html#quirks-mode">quirks mode</a>
-	and has the <a href="https://html.spec.whatwg.org/multipage/origin.html#same-origin">same origin</a> as the imported style sheet,
-	the type of the linked resource is <code>text/css</code>.
-	Otherwise, the type is determined from its <a href="https://html.spec.whatwg.org/multipage/urls-and-fetching.html#content-type">Content-Type metadata</a>.
+	The processing of imported style sheets depends on the actual type of the linked resource:
+
+	* If the resource does not have <l spec=html>[=Content-Type metadata=]</l>,
+		the type is treated as <code>text/css</code>.
+	* If the host document is in [=quirks mode=],
+		and the host document's origin is [=same origin=]
+		with the linked resource [=/response's=] [=response/URL's=] origin,
+		the type is treated as <code>text/css</code>.
+	* Otherwise, the type is determined from its <l spec=html>[=Content-Type metadata=]</l>.
 
 	If the linked resource's type is <code>text/css</code>,
 	it must be interpreted as a CSS style sheet.