Change Runtime::new to take a parent runtime

SpiderMonkey shares some data, such as the self-hosting compartment and read-only atoms, between runtimes - but only if a parent runtime is passed when calling `JS_NewRuntime`. This is important for both memory usage and performance: compiling the self-hosted JS takes more than 30ms on a desktop machine, so doing that every time, say, a worker is created is quite wasteful.

src/rust.rs

@@ -116,8 +116,8 @@ impl Runtime {
     ///
     /// Calling this function concurrently can cause segfaults inside
     /// SpiderMonkey
-    pub unsafe fn new() -> Runtime {
-        let js_runtime = JS_NewRuntime(default_heapsize, ChunkSize as u32, ptr::null_mut());
+    pub unsafe fn new(parent_rt: *mut JSRuntime) -> Runtime {
+        let js_runtime = JS_NewRuntime(default_heapsize, ChunkSize as u32, parent_rt);
         assert!(!js_runtime.is_null());
 
         // Unconstrain the runtime's threshold on nominal heap size, to avoid

tests/callback.rs

@@ -30,7 +30,7 @@ fn callback() {
     unsafe {
         JS_Init();
 
-        let runtime = Runtime::new();
+        let runtime = Runtime::new(ptr::null_mut());
         let context = runtime.cx();
 
         let h_option = OnNewGlobalHookOption::FireOnNewGlobalHook;

tests/evaluate.rs

@@ -19,7 +19,7 @@ use std::ptr;
 fn evaluate() {
     unsafe {
         assert!(JS_Init());
-        let rt = Runtime::new();
+        let rt = Runtime::new(ptr::null_mut());
         let cx = rt.cx();
 
         let global = RootedObject::new(cx,

tests/stack_limit.rs

@@ -20,7 +20,7 @@ fn stack_limit() {
     unsafe {
         assert!(JS_Init());
 
-        let rt = Runtime::new();
+        let rt = Runtime::new(ptr::null_mut());
         let cx = rt.cx();
 
         let h_option = OnNewGlobalHookOption::FireOnNewGlobalHook;

tests/vec_conversion.rs

@@ -25,7 +25,7 @@ fn vec_conversion() {
     unsafe {
         assert!(JS_Init());
 
-        let rt = Runtime::new();
+        let rt = Runtime::new(ptr::null_mut());
         let cx = rt.cx();
 
         let h_option = OnNewGlobalHookOption::FireOnNewGlobalHook;