style: Move root font size handling outside of the cascade.

And merge it with the rest of the code handling root font-size changes.

MozReview-Commit-ID: 3rW1C3mXiMd

2 files changed, 8 insertions, 10 deletions

diff --git a/components/style/matching.rs b/components/style/matching.rs
index 1b9f0307a9d..d59e5517b3d 100644
--- a/components/style/matching.rs
+++ b/components/style/matching.rs
@@ -341,7 +341,6 @@ trait PrivateMatchMethods: TElement {
         if self.is_native_anonymous() || cascade_target == CascadeTarget::EagerPseudo {
             cascade_flags.insert(PROHIBIT_DISPLAY_CONTENTS);
         } else if self.is_root() {
-            debug_assert!(self.owner_doc_matches_for_testing(shared_context.stylist.device()));
             cascade_flags.insert(IS_ROOT_ELEMENT);
         }
 
@@ -563,9 +562,14 @@ trait PrivateMatchMethods: TElement {
                 // If the root font-size changed since last time, and something
                 // in the document did use rem units, ensure we recascade the
                 // entire tree.
-                if old_values.map_or(false, |v| v.get_font().clone_font_size() != new_font_size) &&
-                   device.used_root_font_size() {
-                    child_cascade_requirement = ChildCascadeRequirement::MustCascadeDescendants;
+                if old_values.map_or(true, |v| v.get_font().clone_font_size() != new_font_size) {
+                    // FIXME(emilio): This can fire when called from a document
+                    // from the bfcache (bug 1376897).
+                    debug_assert!(self.owner_doc_matches_for_testing(device));
+                    device.set_root_font_size(new_font_size);
+                    if device.used_root_font_size() {
+                        child_cascade_requirement = ChildCascadeRequirement::MustCascadeDescendants;
+                    }
                 }
             }
         }
diff --git a/components/style/properties/properties.mako.rs b/components/style/properties/properties.mako.rs
index b69b3bacbc8..cd6278167b9 100644
--- a/components/style/properties/properties.mako.rs
+++ b/components/style/properties/properties.mako.rs
@@ -2901,11 +2901,6 @@ pub fn apply_declarations<'a, F, I>(device: &Device,
                                                  error_reporter);
             % endif
             }
-
-            if context.is_root_element {
-                let s = context.style.get_font().clone_font_size();
-                context.device.set_root_font_size(s);
-            }
         % endif
     % endfor
 
@@ -2938,7 +2933,6 @@ pub fn apply_declarations<'a, F, I>(device: &Device,
     style.build()
 }
 
-
 /// See StyleAdjuster::adjust_for_border_width.
 pub fn adjust_border_width(style: &mut StyleBuilder) {
     % for side in ["top", "right", "bottom", "left"]: