Auto merge of #22133 - servo:extern-crate, r=SimonSapin

Use 2018-edition idioms in crates that use that edition

The first commit is almost entirely mechanical, created by running `cargo fix --edition-idioms` and relevant crates. I undid the change of adding an anonymous lifetime parameter in types that have implicit lifetimes parameters, for example replacing `&mut Formatter` with `&mut Formatter<'_>`, because I don’t like it. The remaining changes are, in many places:

* Add `dyn` to trait object types, for example `Rc<gl::Gl>` to `Rc<dyn gl::Gl>`. This change also works in the 2015 edition.
* Remove `extern crate` where is it made unneeded by changes to the import/module system.

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1 files changed, 5 insertions, 5 deletions

diff --git a/components/script/dom/bindings/root.rs b/components/script/dom/bindings/root.rs
index 25b77e052e6..5318eb11e4d 100644
--- a/components/script/dom/bindings/root.rs
+++ b/components/script/dom/bindings/root.rs
@@ -78,14 +78,14 @@ where
 pub unsafe trait StableTraceObject {
     /// Returns a stable trace object which address won't change for the whole
     /// lifetime of the value.
-    fn stable_trace_object(&self) -> *const JSTraceable;
+    fn stable_trace_object(&self) -> *const dyn JSTraceable;
 }
 
 unsafe impl<T> StableTraceObject for Dom<T>
 where
     T: DomObject,
 {
-    fn stable_trace_object<'a>(&'a self) -> *const JSTraceable {
+    fn stable_trace_object<'a>(&'a self) -> *const dyn JSTraceable {
         // The JSTraceable impl for Reflector doesn't actually do anything,
         // so we need this shenanigan to actually trace the reflector of the
         // T pointer in Dom<T>.
@@ -198,7 +198,7 @@ where
 /// See also [*Exact Stack Rooting - Storing a GCPointer on the CStack*]
 /// (https://developer.mozilla.org/en-US/docs/Mozilla/Projects/SpiderMonkey/Internals/GC/Exact_Stack_Rooting).
 pub struct RootCollection {
-    roots: UnsafeCell<Vec<*const JSTraceable>>,
+    roots: UnsafeCell<Vec<*const dyn JSTraceable>>,
 }
 
 thread_local!(static STACK_ROOTS: Cell<Option<*const RootCollection>> = Cell::new(None));
@@ -228,13 +228,13 @@ impl RootCollection {
     }
 
     /// Starts tracking a trace object.
-    unsafe fn root(&self, object: *const JSTraceable) {
+    unsafe fn root(&self, object: *const dyn JSTraceable) {
         debug_assert!(thread_state::get().is_script());
         (*self.roots.get()).push(object);
     }
 
     /// Stops tracking a trace object, asserting if it isn't found.
-    unsafe fn unroot(&self, object: *const JSTraceable) {
+    unsafe fn unroot(&self, object: *const dyn JSTraceable) {
         debug_assert!(thread_state::get().is_script());
         let roots = &mut *self.roots.get();
         match roots.iter().rposition(|r| *r == object) {