From cc31397a2e8d720749d4c93ae5bf48a12d387a53 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Emilio=20Cobos=20=C3=81lvarez?= <emilio@crisal.io>
Date: Tue, 5 Sep 2017 11:52:49 +0200
Subject: [PATCH] style: Don't waste a whole selector map for each class / id
 in the document.

It's just useless.
---
 .../invalidation/element/invalidation_map.rs  | 23 +++++++------------
 .../style/invalidation/element/invalidator.rs | 12 +++++++---
 2 files changed, 17 insertions(+), 18 deletions(-)

diff --git a/components/style/invalidation/element/invalidation_map.rs b/components/style/invalidation/element/invalidation_map.rs
index 68da374ba9e..4a1a092a2aa 100644
--- a/components/style/invalidation/element/invalidation_map.rs
+++ b/components/style/invalidation/element/invalidation_map.rs
@@ -139,10 +139,10 @@ impl SelectorMapEntry for StateDependency {
 pub struct InvalidationMap {
     /// A map from a given class name to all the selectors with that class
     /// selector.
-    pub class_to_selector: MaybeCaseInsensitiveHashMap<Atom, SelectorMap<Dependency>>,
+    pub class_to_selector: MaybeCaseInsensitiveHashMap<Atom, SmallVec<[Dependency; 1]>>,
     /// A map from a given id to all the selectors with that ID in the
     /// stylesheets currently applying to the document.
-    pub id_to_selector: MaybeCaseInsensitiveHashMap<Atom, SelectorMap<Dependency>>,
+    pub id_to_selector: MaybeCaseInsensitiveHashMap<Atom, SmallVec<[Dependency; 1]>>,
     /// A map of all the state dependencies.
     pub state_affecting_selectors: SelectorMap<StateDependency>,
     /// A map of other attribute affecting selectors.
@@ -245,21 +245,21 @@ impl InvalidationMap {
             for class in compound_visitor.classes {
                 self.class_to_selector
                     .entry(class, quirks_mode)
-                    .or_insert_with(SelectorMap::new)
-                    .insert(Dependency {
+                    .or_insert_with(SmallVec::new)
+                    .push(Dependency {
                         selector: selector.clone(),
                         selector_offset: sequence_start,
-                    }, quirks_mode);
+                    })
             }
 
             for id in compound_visitor.ids {
                 self.id_to_selector
                     .entry(id, quirks_mode)
-                    .or_insert_with(SelectorMap::new)
-                    .insert(Dependency {
+                    .or_insert_with(SmallVec::new)
+                    .push(Dependency {
                         selector: selector.clone(),
                         selector_offset: sequence_start,
-                    }, quirks_mode);
+                    })
             }
 
             if !compound_visitor.state.is_empty() {
@@ -299,14 +299,7 @@ impl InvalidationMap {
         let mut n = 0;
 
         n += self.class_to_selector.malloc_shallow_size_of_hash(malloc_enclosing_size_of);
-        for (_, val) in self.class_to_selector.iter() {
-            n += val.malloc_size_of_children(malloc_enclosing_size_of);
-        }
-
         n += self.id_to_selector.malloc_shallow_size_of_hash(malloc_enclosing_size_of);
-        for (_, val) in self.id_to_selector.iter() {
-            n += val.malloc_size_of_children(malloc_enclosing_size_of);
-        }
 
         n += self.state_affecting_selectors.malloc_size_of_children(malloc_enclosing_size_of);
 
diff --git a/components/style/invalidation/element/invalidator.rs b/components/style/invalidation/element/invalidator.rs
index 00c3e3f8954..4d4ebff9717 100644
--- a/components/style/invalidation/element/invalidator.rs
+++ b/components/style/invalidation/element/invalidator.rs
@@ -792,20 +792,26 @@ impl<'a, 'b: 'a, E> InvalidationCollector<'a, 'b, E>
         let removed_id = self.removed_id;
         if let Some(ref id) = removed_id {
             if let Some(deps) = map.id_to_selector.get(id, quirks_mode) {
-                self.collect_dependencies_in_map(deps)
+                for dep in deps {
+                    self.scan_dependency(dep, false);
+                }
             }
         }
 
         let added_id = self.added_id;
         if let Some(ref id) = added_id {
             if let Some(deps) = map.id_to_selector.get(id, quirks_mode) {
-                self.collect_dependencies_in_map(deps)
+                for dep in deps {
+                    self.scan_dependency(dep, false);
+                }
             }
         }
 
         for class in self.classes_added.iter().chain(self.classes_removed.iter()) {
             if let Some(deps) = map.class_to_selector.get(class, quirks_mode) {
-                self.collect_dependencies_in_map(deps)
+                for dep in deps {
+                    self.scan_dependency(dep, false);
+                }
             }
         }