servo: Merge #16972 - style: Move all the style sharing code outside matching.rs (from emilio:sanity-is-important-most-of-the-time); r=bholley

This is just a code health change. I want to move it away to keep matching.rs as
simple as possible.

Source-Repo: https://github.com/servo/servo
Source-Revision: 03fbea4ec8af3ef6c5c621974b3c52cd755ed287

Author: emilio

servo/components/style/context.rs

@@ -17,13 +17,13 @@ use euclid::Size2D;
 use fnv::FnvHashMap;
 use font_metrics::FontMetricsProvider;
 #[cfg(feature = "gecko")] use gecko_bindings::structs;
-use matching::StyleSharingCandidateCache;
 #[cfg(feature = "servo")] use parking_lot::RwLock;
 #[cfg(feature = "gecko")] use properties::ComputedValues;
 use selector_parser::SnapshotMap;
 use selectors::matching::ElementSelectorFlags;
 #[cfg(feature = "servo")] use servo_config::opts;
 use shared_lock::StylesheetGuards;
+use sharing::StyleSharingCandidateCache;
 #[cfg(feature = "servo")] use std::collections::HashMap;
 #[cfg(feature = "gecko")] use std::env;
 use std::fmt;

servo/components/style/lib.rs

@@ -121,6 +121,7 @@ pub mod rule_tree;
 pub mod scoped_tls;
 pub mod selector_parser;
 pub mod shared_lock;
+pub mod sharing;
 pub mod stylist;
 #[cfg(feature = "servo")] #[allow(unsafe_code)] pub mod servo;
 pub mod sequential;