Add task_source directory

Use DOMManipulationTaskSource whenever possible

components/script/task_source/user_interaction.rs

@@ -0,0 +1,21 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use script_thread::{CommonScriptMsg, MainThreadScriptMsg, ScriptChan};
+use std::sync::mpsc::Sender;
+
+#[derive(JSTraceable)]
+pub struct UserInteractionTaskSource(pub Sender<MainThreadScriptMsg>);
+
+impl ScriptChan for UserInteractionTaskSource {
+    fn send(&self, msg: CommonScriptMsg) -> Result<(), ()> {
+        let UserInteractionTaskSource(ref chan) = *self;
+        chan.send(MainThreadScriptMsg::Common(msg)).map_err(|_| ())
+    }
+
+    fn clone(&self) -> Box<ScriptChan + Send> {
+        let UserInteractionTaskSource(ref chan) = *self;
+        box UserInteractionTaskSource((*chan).clone())
+    }
+}