style: Implement the body text color quirk in a more straight-forward way.

This avoids grabbing the document when values that inherit from the body,
whatever that means, aren't under the body.

In that case we'll get a semi-random value, but that's also mishandled by Gecko
anyways (and probably Blink, though haven't tested), and doesn't really make
much sense.

components/style/matching.rs

@@ -7,7 +7,8 @@
 #![allow(unsafe_code)]
 #![deny(missing_docs)]
 
-use context::{ElementCascadeInputs, SelectorFlagsMap, SharedStyleContext, StyleContext};
+use context::{ElementCascadeInputs, QuirksMode, SelectorFlagsMap};
+use context::{SharedStyleContext, StyleContext};
 use data::ElementData;
 use dom::TElement;
 use invalidation::element::restyle_hints::{RESTYLE_CSS_ANIMATIONS, RESTYLE_CSS_TRANSITIONS};
@@ -586,6 +587,21 @@ pub trait MatchMethods : TElement {
             }
         }
 
+        if context.shared.stylist.quirks_mode() == QuirksMode::Quirks {
+            if self.is_html_document_body_element() {
+                // NOTE(emilio): We _could_ handle dynamic changes to it if it
+                // changes and before we reach our children the cascade stops,
+                // but we don't track right now whether we use the document body
+                // color, and nobody else handles that properly anyway.
+
+                let device = context.shared.stylist.device();
+
+                // Needed for the "inherit from body" quirk.
+                let text_color = new_primary_style.get_color().clone_color();
+                device.set_body_text_color(text_color);
+            }
+        }
+
         // Don't accumulate damage if we're in a forgetful traversal.
         if context.shared.traversal_flags.contains(traversal_flags::Forgetful) {
             return ChildCascadeRequirement::MustCascadeChildren;