Remove the script listener thread (fixes #11345).

We needed a separate thread in the chrome process because communication to the
compositor is done through a trait object, and cross-process virtual calls are
forbidden.

Also, the fact that these messages are ultimately handled by the compositor is
an implementation detail; conceptually, the relevant constellation is supposed
to handle these messages.

So instead, the script thread will now send the messages to the constellation,
which will ask the compositor to handle them.

components/script_traits/lib.rs

@@ -57,7 +57,7 @@ use std::sync::mpsc::{Sender, Receiver};
 use url::Url;
 use util::ipc::OptionalOpaqueIpcSender;
 
-pub use script_msg::{LayoutMsg, ScriptMsg};
+pub use script_msg::{LayoutMsg, ScriptMsg, EventResult};
 
 /// The address of a node. Layout sends these back. They must be validated via
 /// `from_untrusted_node_address` before they can be used, because we do not trust layout.
@@ -304,8 +304,6 @@ pub struct InitialScriptState {
     /// The subpage ID of this pipeline to create in its pipeline parent.
     /// If `None`, this is the root.
     pub parent_info: Option<(PipelineId, SubpageId)>,
-    /// The compositor.
-    pub compositor: IpcSender<ScriptToCompositorMsg>,
     /// A channel with which messages can be sent to us (the script thread).
     pub control_chan: IpcSender<ConstellationControlMsg>,
     /// A port on which messages sent by the constellation to script can be received.
@@ -349,41 +347,6 @@ pub trait ScriptThreadFactory {
               -> (Sender<Self::Message>, Receiver<Self::Message>);
 }
 
-/// Messages sent from the script thread to the compositor
-#[derive(Deserialize, Serialize)]
-pub enum ScriptToCompositorMsg {
-    /// Scroll a page in a window
-    ScrollFragmentPoint(PipelineId, LayerId, Point2D<f32>, bool),
-    /// Set title of current page
-    /// https://html.spec.whatwg.org/multipage/#document.title
-    SetTitle(PipelineId, Option<String>),
-    /// Send a key event
-    SendKeyEvent(Key, KeyState, KeyModifiers),
-    /// Get Window Informations size and position
-    GetClientWindow(IpcSender<(Size2D<u32>, Point2D<i32>)>),
-    /// Move the window to a point
-    MoveTo(Point2D<i32>),
-    /// Resize the window to size
-    ResizeTo(Size2D<u32>),
-    /// Script has handled a touch event, and either prevented or allowed default actions.
-    TouchEventProcessed(EventResult),
-    /// Get Scroll Offset
-    GetScrollOffset(PipelineId, LayerId, IpcSender<Point2D<f32>>),
-    /// Requests that the compositor shut down.
-    Exit,
-    /// Allow the compositor to free script-specific resources.
-    Exited,
-}
-
-/// Whether a DOM event was prevented by web content
-#[derive(Deserialize, Serialize)]
-pub enum EventResult {
-    /// Allowed by web content
-    DefaultAllowed,
-    /// Prevented by web content
-    DefaultPrevented,
-}
-
 /// Whether the sandbox attribute is present for an iframe element
 #[derive(PartialEq, Eq, Copy, Clone, Debug, Deserialize, Serialize)]
 pub enum IFrameSandboxState {