servo: Merge #12448 - Implement file reading task source (from jdm:file-reading-task-source-2); r=KiChjang

Implement the task source API for the File Reader task source, enabling using task sources from non-main threads.

---
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix (partially) #7959 (github issue number if applicable).
- [X] These changes do not require tests because they're refactoring existing code

Source-Repo: https://github.com/servo/servo
Source-Revision: 48a912f57ec51e55e7905983b2bf368a07a9902f

servo/components/script/task_source/mod.rs

@@ -8,10 +8,17 @@ pub mod history_traversal;
 pub mod networking;
 pub mod user_interaction;
 
-use dom::window::Window;
-use script_thread::Runnable;
+use dom::bindings::global::GlobalRef;
+use script_thread::{Runnable, RunnableWrapper};
 use std::result::Result;
 
 pub trait TaskSource {
-    fn queue<T: Runnable + Send + 'static>(&self, msg: Box<T>, window: &Window) -> Result<(), ()>;
+    fn queue_with_wrapper<T>(&self,
+                             msg: Box<T>,
+                             wrapper: &RunnableWrapper)
+                             -> Result<(), ()>
+                             where T: Runnable + Send + 'static;
+    fn queue<T: Runnable + Send + 'static>(&self, msg: Box<T>, global: GlobalRef) -> Result<(), ()> {
+        self.queue_with_wrapper(msg, &global.get_runnable_wrapper())
+    }
 }