Store the layout-to-constellation sender in the script thread.

This will allow the script thread to spawn layout threads independently.

components/constellation/pipeline.rs

@@ -165,7 +165,6 @@ impl Pipeline {
                     load_data: state.load_data.clone(),
                     window_size: window_size,
                     pipeline_port: pipeline_port,
-                    layout_to_constellation_chan: state.layout_to_constellation_chan.clone(),
                     content_process_shutdown_chan: Some(layout_content_process_shutdown_chan.clone()),
                     layout_threads: PREFS.get("layout.threads").as_u64().expect("count") as usize,
                 };
@@ -424,6 +423,7 @@ impl UnprivilegedPipelineContent {
             control_chan: self.script_chan.clone(),
             control_port: self.script_port,
             constellation_chan: self.constellation_chan,
+            layout_to_constellation_chan: self.layout_to_constellation_chan.clone(),
             scheduler_chan: self.scheduler_chan,
             bluetooth_thread: self.bluetooth_thread,
             resource_threads: self.resource_threads,

components/script/script_thread.rs

@@ -82,7 +82,7 @@ use script_layout_interface::message::{self, NewLayoutThreadInfo, ReflowQueryTyp
 use script_runtime::{CommonScriptMsg, ScriptChan, ScriptThreadEventCategory, EnqueuedPromiseCallback};
 use script_runtime::{ScriptPort, StackRootTLS, get_reports, new_rt_and_cx, PromiseJobQueue};
 use script_traits::{CompositorEvent, ConstellationControlMsg, EventResult};
-use script_traits::{InitialScriptState, LoadData, MouseButton, MouseEventType, MozBrowserEvent};
+use script_traits::{InitialScriptState, LayoutMsg, LoadData, MouseButton, MouseEventType, MozBrowserEvent};
 use script_traits::{NewLayoutInfo, ScriptMsg as ConstellationMsg};
 use script_traits::{ScriptThreadFactory, TimerEvent, TimerEventRequest, TimerSource};
 use script_traits::{TouchEventType, TouchId, UntrustedNodeAddress, WindowSizeData, WindowSizeType};
@@ -434,6 +434,9 @@ pub struct ScriptThread {
     /// For communicating load url messages to the constellation
     constellation_chan: IpcSender<ConstellationMsg>,
 
+    /// A sender for new layout threads to communicate to the constellation.
+    layout_to_constellation_chan: IpcSender<LayoutMsg>,
+
     /// The port on which we receive messages from the image cache
     image_cache_port: Receiver<ImageCacheResult>,
 
@@ -681,6 +684,8 @@ impl ScriptThread {
             content_process_shutdown_chan: state.content_process_shutdown_chan,
 
             promise_job_queue: PromiseJobQueue::new(),
+
+            layout_to_constellation_chan: state.layout_to_constellation_chan,
         }
     }
 
@@ -1179,7 +1184,6 @@ impl ScriptThread {
             load_data,
             window_size,
             pipeline_port,
-            layout_to_constellation_chan,
             content_process_shutdown_chan,
             layout_threads,
         } = new_layout_info;
@@ -1193,7 +1197,7 @@ impl ScriptThread {
             is_parent: false,
             layout_pair: layout_pair,
             pipeline_port: pipeline_port,
-            constellation_chan: layout_to_constellation_chan,
+            constellation_chan: self.layout_to_constellation_chan.clone(),
             script_chan: self.control_chan.clone(),
             image_cache_thread: self.image_cache_thread.clone(),
             content_process_shutdown_chan: content_process_shutdown_chan,

components/script_traits/lib.rs

@@ -177,8 +177,6 @@ pub struct NewLayoutInfo {
     pub window_size: Option<WindowSizeData>,
     /// A port on which layout can receive messages from the pipeline.
     pub pipeline_port: IpcReceiver<LayoutControlMsg>,
-    /// A sender for the layout thread to communicate to the constellation.
-    pub layout_to_constellation_chan: IpcSender<LayoutMsg>,
     /// A shutdown channel so that layout can tell the content process to shut down when it's done.
     pub content_process_shutdown_chan: Option<IpcSender<()>>,
     /// Number of threads to use for layout.
@@ -450,6 +448,8 @@ pub struct InitialScriptState {
     pub control_port: IpcReceiver<ConstellationControlMsg>,
     /// A channel on which messages can be sent to the constellation from script.
     pub constellation_chan: IpcSender<ScriptMsg>,
+    /// A sender for the layout thread to communicate to the constellation.
+    pub layout_to_constellation_chan: IpcSender<LayoutMsg>,
     /// A channel to schedule timer events.
     pub scheduler_chan: IpcSender<TimerEventRequest>,
     /// A channel to the resource manager thread.