Provide webrender_api::RenderApiSender to ScriptThread and DOM Window

This will allow the HTMLMediaElement later to get a handle to the
RenderApi for rendering video frames.

At a later time, all media handling should be moved to its own
thread/process that is communicated with via IPC. At that point this
can be removed again.

Original-patch-by: Sebastian Dröge <sebastian@centricular.com>

components/constellation/pipeline.rs

@@ -517,6 +517,7 @@ impl UnprivilegedPipelineContent {
                 webgl_chan: self.webgl_chan,
                 webvr_chan: self.webvr_chan,
                 webrender_document: self.webrender_document,
+                webrender_api_sender: self.webrender_api_sender.clone(),
             },
             self.load_data.clone(),
         );

components/script/dom/window.rs

@@ -132,7 +132,9 @@ use time;
 use timers::{IsInterval, TimerCallback};
 use url::Position;
 use webdriver_handlers::jsval_to_webdriver;
-use webrender_api::{ExternalScrollId, DeviceIntPoint, DeviceUintSize, DocumentId};
+use webrender_api::{
+    DeviceIntPoint, DeviceUintSize, DocumentId, ExternalScrollId, RenderApiSender,
+};
 use webvr_traits::WebVRMsg;
 
 /// Current state of the window object
@@ -308,6 +310,17 @@ pub struct Window {
 
     /// Flag to identify whether mutation observers are present(true)/absent(false)
     exists_mut_observer: Cell<bool>,
+    /// Webrender API Sender
+    #[ignore_malloc_size_of = "defined in webrender_api"]
+    webrender_api_sender: RenderApiSender,
+}
+
+// FIXME(victor):  this doesn't belong here
+#[allow(unsafe_code)]
+unsafe impl ::dom::bindings::trace::JSTraceable for RenderApiSender {
+    unsafe fn trace(&self, _trc: *mut ::js::jsapi::JSTracer) {
+        // Do nothing
+    }
 }
 
 impl Window {
@@ -483,6 +496,10 @@ impl Window {
         }
         self.add_pending_reflow();
     }
+
+    pub fn get_webrender_api_sender(&self) -> RenderApiSender {
+        self.webrender_api_sender.clone()
+    }
 }
 
 // https://html.spec.whatwg.org/multipage/#atob
@@ -2083,6 +2100,7 @@ impl Window {
         webvr_chan: Option<IpcSender<WebVRMsg>>,
         microtask_queue: Rc<MicrotaskQueue>,
         webrender_document: DocumentId,
+        webrender_api_sender: RenderApiSender,
     ) -> DomRoot<Self> {
         let layout_rpc: Box<LayoutRPC + Send> = {
             let (rpc_send, rpc_recv) = channel();
@@ -2161,6 +2179,7 @@ impl Window {
             paint_worklet: Default::default(),
             webrender_document,
             exists_mut_observer: Cell::new(false),
+            webrender_api_sender,
         });
 
         unsafe { WindowBinding::Wrap(runtime.cx(), win) }

components/script/script_thread.rs

@@ -130,7 +130,7 @@ use time::{get_time, precise_time_ns, Tm};
 use url::Position;
 use url::percent_encoding::percent_decode;
 use webdriver_handlers;
-use webrender_api::DocumentId;
+use webrender_api::{DocumentId, RenderApiSender};
 use webvr_traits::{WebVREvent, WebVRMsg};
 
 pub type ImageCacheMsg = (PipelineId, PendingImageResponse);
@@ -591,6 +591,9 @@ pub struct ScriptThread {
 
     /// The Webrender Document ID associated with this thread.
     webrender_document: DocumentId,
+
+    /// FIXME(victor):
+    webrender_api_sender: RenderApiSender,
 }
 
 /// In the event of thread panic, all data on the stack runs its destructor. However, there
@@ -1063,6 +1066,7 @@ impl ScriptThread {
             custom_element_reaction_stack: CustomElementReactionStack::new(),
 
             webrender_document: state.webrender_document,
+            webrender_api_sender: state.webrender_api_sender,
         }
     }
 
@@ -2584,6 +2588,7 @@ impl ScriptThread {
             self.webvr_chan.clone(),
             self.microtask_queue.clone(),
             self.webrender_document,
+            self.webrender_api_sender.clone(),
         );
 
         // Initialize the browsing context for the window.

components/script_traits/lib.rs

@@ -72,7 +72,9 @@ use style_traits::CSSPixel;
 use style_traits::SpeculativePainter;
 use style_traits::cursor::CursorKind;
 use webdriver_msg::{LoadStatus, WebDriverScriptCommand};
-use webrender_api::{ExternalScrollId, DevicePixel, DeviceUintSize, DocumentId, ImageKey};
+use webrender_api::{
+    DevicePixel, DeviceUintSize, DocumentId, ExternalScrollId, ImageKey, RenderApiSender,
+};
 use webvr_traits::{WebVREvent, WebVRMsg};
 
 pub use script_msg::{LayoutMsg, ScriptMsg, EventResult, LogEntry};
@@ -588,6 +590,8 @@ pub struct InitialScriptState {
     pub webvr_chan: Option<IpcSender<WebVRMsg>>,
     /// The Webrender document ID associated with this thread.
     pub webrender_document: DocumentId,
+    /// FIXME(victor): The Webrender API sender in this constellation's pipeline
+    pub webrender_api_sender: RenderApiSender,
 }
 
 /// This trait allows creating a `ScriptThread` without depending on the `script`