Auto merge of #15888 - emilio:caching, r=Ms2ger

style: Simplify style sharing code.

No functional changes, just some code cleanup.

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components/style/cache.rs

@@ -11,14 +11,14 @@ use std::slice::{Iter, IterMut};
 /// A LRU cache used to store a set of at most `n` elements at the same time.
 ///
 /// Currently used for the style sharing candidate cache.
-pub struct LRUCache<K, V> {
-    entries: Vec<(K, V)>,
+pub struct LRUCache<K> {
+    entries: Vec<K>,
     cache_size: usize,
 }
 
-impl<K: PartialEq, V: Clone> LRUCache<K, V> {
+impl<K: PartialEq> LRUCache<K> {
     /// Create a new LRU cache with `size` elements at most.
-    pub fn new(size: usize) -> LRUCache<K, V> {
+    pub fn new(size: usize) -> Self {
         LRUCache {
           entries: vec![],
           cache_size: size,
@@ -27,54 +27,30 @@ impl<K: PartialEq, V: Clone> LRUCache<K, V> {
 
     #[inline]
     /// Touch a given position, and put it in the last item on the list.
-    pub fn touch(&mut self, pos: usize) -> &V {
+    pub fn touch(&mut self, pos: usize) {
         let last_index = self.entries.len() - 1;
         if pos != last_index {
             let entry = self.entries.remove(pos);
             self.entries.push(entry);
         }
-        &self.entries[last_index].1
     }
 
     /// Iterate over the contents of this cache.
-    pub fn iter(&self) -> Iter<(K, V)> {
+    pub fn iter(&self) -> Iter<K> {
         self.entries.iter()
     }
 
     /// Iterate mutably over the contents of this cache.
-    pub fn iter_mut(&mut self) -> IterMut<(K, V)> {
+    pub fn iter_mut(&mut self) -> IterMut<K> {
         self.entries.iter_mut()
     }
 
-    /// Insert a given key and value in the cache.
-    pub fn insert(&mut self, key: K, val: V) {
+    /// Insert a given key in the cache.
+    pub fn insert(&mut self, key: K) {
         if self.entries.len() == self.cache_size {
             self.entries.remove(0);
         }
-        self.entries.push((key, val));
-    }
-
-    /// Try to find a key in the cache.
-    pub fn find(&mut self, key: &K) -> Option<V> {
-        match self.entries.iter().position(|&(ref k, _)| key == k) {
-            Some(pos) => Some(self.touch(pos).clone()),
-            None      => None,
-        }
-    }
-
-    /// Try to find a given key, or create a given item with that key executing
-    /// `blk`.
-    pub fn find_or_create<F>(&mut self, key: K, mut blk: F) -> V
-        where F: FnMut() -> V,
-    {
-        match self.entries.iter().position(|&(ref k, _)| *k == key) {
-            Some(pos) => self.touch(pos).clone(),
-            None => {
-                let val = blk();
-                self.insert(key, val.clone());
-                val
-            }
-        }
+        self.entries.push(key);
     }
 
     /// Evict all elements from the cache.

components/style/matching.rs

@@ -110,7 +110,7 @@ impl<E: TElement> PartialEq<StyleSharingCandidate<E>> for StyleSharingCandidate<
 /// Note that this cache is flushed every time we steal work from the queue, so
 /// storing nodes here temporarily is safe.
 pub struct StyleSharingCandidateCache<E: TElement> {
-    cache: LRUCache<StyleSharingCandidate<E>, ()>,
+    cache: LRUCache<StyleSharingCandidate<E>>,
 }
 
 /// A cache miss result.
@@ -366,7 +366,7 @@ impl<E: TElement> StyleSharingCandidateCache<E> {
         }
     }
 
-    fn iter_mut(&mut self) -> IterMut<(StyleSharingCandidate<E>, ())> {
+    fn iter_mut(&mut self) -> IterMut<StyleSharingCandidate<E>> {
         self.cache.iter_mut()
     }
 
@@ -410,7 +410,7 @@ impl<E: TElement> StyleSharingCandidateCache<E> {
             element: unsafe { SendElement::new(*element) },
             common_style_affecting_attributes: None,
             class_attributes: None,
-        }, ());
+        });
     }
 
     /// Touch a given index in the style sharing candidate cache.
@@ -881,8 +881,10 @@ pub trait MatchMethods : TElement {
         }
 
         let mut should_clear_cache = false;
-        for (i, &mut (ref mut candidate, ())) in style_sharing_candidate_cache.iter_mut().enumerate() {
-            let sharing_result = self.share_style_with_candidate_if_possible(shared_context, candidate);
+        for (i, candidate) in style_sharing_candidate_cache.iter_mut().enumerate() {
+            let sharing_result =
+                self.share_style_with_candidate_if_possible(shared_context,
+                                                            candidate);
             match sharing_result {
                 Ok(shared_style) => {
                     // Yay, cache hit. Share the style.