geckolib: move NUM_THREADS from style to geckolib

This change eliminates some gecko-only configuration in the style
component and moves NUM_THREADS closer to its only uses.

Cargo.lock

@@ -2719,7 +2719,6 @@ dependencies = [
  "nsstring_vendor 0.1.0",
  "num-integer 0.1.32 (registry+https://github.com/rust-lang/crates.io-index)",
  "num-traits 0.1.36 (registry+https://github.com/rust-lang/crates.io-index)",
- "num_cpus 1.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "ordered-float 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "owning_ref 0.2.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "parking_lot 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",

components/style/Cargo.toml

@@ -13,7 +13,7 @@ path = "lib.rs"
 doctest = false
 
 [features]
-gecko = ["nsstring_vendor", "num_cpus", "rayon/unstable"]
+gecko = ["nsstring_vendor", "rayon/unstable"]
 use_bindgen = ["bindgen", "regex"]
 servo = ["serde/unstable", "serde", "serde_derive", "heapsize_derive",
          "style_traits/servo", "servo_atoms", "html5ever-atoms",
@@ -57,10 +57,6 @@ servo_url = {path = "../url"}
 time = "0.1"
 unicode-segmentation = "1.0"
 
-[dependencies.num_cpus]
-optional = true
-version = "1.0"
-
 [target.'cfg(windows)'.dependencies]
 kernel32-sys = "0.2"
 

components/style/gecko/data.rs

@@ -11,12 +11,9 @@ use gecko_bindings::bindings::RawServoStyleSet;
 use gecko_bindings::structs::RawGeckoPresContextOwned;
 use gecko_bindings::sugar::ownership::{HasBoxFFI, HasFFI, HasSimpleFFI};
 use media_queries::Device;
-use num_cpus;
 use parking_lot::RwLock;
 use properties::ComputedValues;
-use std::cmp;
 use std::collections::HashMap;
-use std::env;
 use std::sync::Arc;
 use std::sync::mpsc::{Receiver, Sender, channel};
 use stylesheets::Stylesheet;
@@ -53,16 +50,6 @@ pub struct PerDocumentStyleDataImpl {
 /// and unexpected races while trying to mutate it.
 pub struct PerDocumentStyleData(AtomicRefCell<PerDocumentStyleDataImpl>);
 
-lazy_static! {
-    /// The number of layout threads, computed statically.
-    pub static ref NUM_THREADS: usize = {
-        match env::var("STYLO_THREADS").map(|s| s.parse::<usize>().expect("invalid STYLO_THREADS")) {
-            Ok(num) => num,
-            _ => cmp::max(num_cpus::get() * 3 / 4, 1),
-        }
-    };
-}
-
 impl PerDocumentStyleData {
     /// Create a dummy `PerDocumentStyleData`.
     pub fn new(pres_context: RawGeckoPresContextOwned) -> Self {

components/style/lib.rs

@@ -61,7 +61,6 @@ extern crate matches;
 #[cfg(feature = "gecko")] extern crate nsstring_vendor as nsstring;
 extern crate num_integer;
 extern crate num_traits;
-#[cfg(feature = "gecko")] extern crate num_cpus;
 extern crate ordered_float;
 extern crate owning_ref;
 extern crate parking_lot;

ports/geckolib/glue.rs

@@ -8,11 +8,13 @@ use cssparser::Parser;
 use cssparser::ToCss as ParserToCss;
 use env_logger::LogBuilder;
 use euclid::Size2D;
+use num_cpus;
 use parking_lot::RwLock;
 use rayon;
 use selectors::Element;
 use servo_url::ServoUrl;
 use std::borrow::Cow;
+use std::cmp;
 use std::env;
 use std::fmt::Write;
 use std::mem;
@@ -24,7 +26,7 @@ use style::context::{ThreadLocalStyleContext, ThreadLocalStyleContextCreationInf
 use style::data::{ElementData, ElementStyles, RestyleData};
 use style::dom::{ShowSubtreeData, TElement, TNode};
 use style::error_reporting::StdoutErrorReporter;
-use style::gecko::data::{NUM_THREADS, PerDocumentStyleData, PerDocumentStyleDataImpl};
+use style::gecko::data::{PerDocumentStyleData, PerDocumentStyleDataImpl};
 use style::gecko::restyle_damage::GeckoRestyleDamage;
 use style::gecko::selector_parser::{SelectorImpl, PseudoElement};
 use style::gecko::traversal::RecalcStyleOnly;
@@ -91,6 +93,16 @@ use stylesheet_loader::StylesheetLoader;
  * depend on but good enough for our purposes.
  */
 
+lazy_static! {
+    /// The number of layout threads, computed statically.
+    static ref NUM_THREADS: usize = {
+        match env::var("STYLO_THREADS").map(|s| s.parse::<usize>().expect("invalid STYLO_THREADS")) {
+            Ok(num) => num,
+            _ => cmp::max(num_cpus::get() * 3 / 4, 1),
+        }
+    };
+}
+
 lazy_static! {
     static ref STYLE_THREAD_POOL: Option<rayon::ThreadPool> = {
         let num_threads = *NUM_THREADS;

ports/geckolib/lib.rs

@@ -12,6 +12,7 @@ extern crate euclid;
 #[macro_use] extern crate lazy_static;
 extern crate libc;
 #[macro_use] extern crate log;
+extern crate num_cpus;
 extern crate parking_lot;
 extern crate rayon;
 extern crate selectors;