Move util::tid to style

components/style/tid.rs

@@ -0,0 +1,26 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use std::cell::RefCell;
+use std::rc::Rc;
+use std::sync::atomic::{ATOMIC_USIZE_INIT, AtomicUsize, Ordering};
+
+static NEXT_TID: AtomicUsize = ATOMIC_USIZE_INIT;
+
+thread_local!(static TASK_LOCAL_TID: Rc<RefCell<Option<usize>>> = Rc::new(RefCell::new(None)));
+
+/// Every thread gets one, that's unique.
+pub fn tid() -> usize {
+    TASK_LOCAL_TID.with(|ref k| {
+        let ret =
+            match *k.borrow() {
+                None => NEXT_TID.fetch_add(1, Ordering::SeqCst),
+                Some(x) => x,
+            };
+
+        *k.borrow_mut() = Some(ret);
+
+        ret
+    })
+}