servo: Merge #20222 - Do not disable thread pool in the parent process (from upsuper:chrome-thread-pool); r=bholley

This is the Servo side change of [bug 1375913](https://bugzilla.mozilla.org/show_bug.cgi?id=1375913).

Source-Repo: https://github.com/servo/servo
Source-Revision: 3b96fb2cbe8754b30646e8bd914806048c0b6db2

--HG--
extra : subtree_source : https%3A//hg.mozilla.org/projects/converted-servo-linear
extra : subtree_revision : 0adb8753d1c45b6a089f758bc9e5217aaec749cd

servo/components/style/gecko/generated/bindings.rs

@@ -1684,9 +1684,6 @@ extern "C" {
 extern "C" {
     pub fn Gecko_RegisterNamespace(ns: *mut nsAtom) -> i32;
 }
-extern "C" {
-    pub fn Gecko_ShouldCreateStyleThreadPool() -> bool;
-}
 extern "C" {
     pub fn Gecko_Construct_Default_nsStyleFont(
         ptr: *mut nsStyleFont,

servo/components/style/gecko/global_style_data.rs

@@ -5,7 +5,6 @@
 //! Global style data
 
 use context::StyleSystemOptions;
-use gecko_bindings::bindings;
 use gecko_bindings::bindings::{Gecko_RegisterProfilerThread, Gecko_UnregisterProfilerThread};
 use gecko_bindings::bindings::Gecko_SetJemallocThreadLocalArena;
 use num_cpus;
@@ -82,7 +81,7 @@ lazy_static! {
             }
         }
 
-        let pool = if num_threads < 1 || unsafe { !bindings::Gecko_ShouldCreateStyleThreadPool() } {
+        let pool = if num_threads < 1 {
             None
         } else {
             let workers = rayon::ThreadPoolBuilder::new()