servo: Merge #13996 - Implement synchronous about:blank loading (from servo:about-blank); r=Ms2ger,jdm,asajeffrey,nox

Based on initial work by jdm in <https://github.com/servo/servo/pull/8600>.

Source-Repo: https://github.com/servo/servo
Source-Revision: 0d896a8d820e31037d536f133b5a8b8c43c2e1a2

servo/components/constellation/constellation.rs

@@ -42,7 +42,7 @@ use rand::{Rng, SeedableRng, StdRng, random};
 use script_traits::{AnimationState, AnimationTickType, CompositorEvent};
 use script_traits::{ConstellationControlMsg, ConstellationMsg as FromCompositorMsg};
 use script_traits::{DocumentState, LayoutControlMsg, LoadData};
-use script_traits::{IFrameLoadInfo, IFrameSandboxState, TimerEventRequest};
+use script_traits::{IFrameLoadInfo, IFrameLoadInfoWithData, IFrameSandboxState, TimerEventRequest};
 use script_traits::{LayoutMsg as FromLayoutMsg, ScriptMsg as FromScriptMsg, ScriptThreadFactory};
 use script_traits::{LogEntry, ServiceWorkerMsg, webdriver_msg};
 use script_traits::{MozBrowserErrorType, MozBrowserEvent, WebDriverCommandMsg, WindowSizeData};
@@ -914,11 +914,17 @@ impl<Message, LTF, STF> Constellation<Message, LTF, STF>
             }
             FromScriptMsg::ScriptLoadedURLInIFrame(load_info) => {
                 debug!("constellation got iframe URL load message {:?} {:?} {:?}",
-                       load_info.parent_pipeline_id,
+                       load_info.info.parent_pipeline_id,
                        load_info.old_pipeline_id,
-                       load_info.new_pipeline_id);
+                       load_info.info.new_pipeline_id);
                 self.handle_script_loaded_url_in_iframe_msg(load_info);
             }
+            FromScriptMsg::ScriptLoadedAboutBlankInIFrame(load_info, lc) => {
+                debug!("constellation got loaded `about:blank` in iframe message {:?} {:?}",
+                       load_info.parent_pipeline_id,
+                       load_info.new_pipeline_id);
+                self.handle_script_loaded_about_blank_in_iframe_msg(load_info, lc);
+            }
             FromScriptMsg::ChangeRunningAnimationsState(pipeline_id, animation_state) => {
                 self.handle_change_running_animations_state(pipeline_id, animation_state)
             }
@@ -1363,14 +1369,14 @@ impl<Message, LTF, STF> Constellation<Message, LTF, STF>
     // will result in a new pipeline being spawned and a frame tree being added to
     // parent_pipeline_id's frame tree's children. This message is never the result of a
     // page navigation.
-    fn handle_script_loaded_url_in_iframe_msg(&mut self, load_info: IFrameLoadInfo) {
+    fn handle_script_loaded_url_in_iframe_msg(&mut self, load_info: IFrameLoadInfoWithData) {
         let (load_data, window_size, is_private) = {
             let old_pipeline = load_info.old_pipeline_id
                 .and_then(|old_pipeline_id| self.pipelines.get(&old_pipeline_id));
 
-            let source_pipeline =  match self.pipelines.get(&load_info.parent_pipeline_id) {
+            let source_pipeline = match self.pipelines.get(&load_info.info.parent_pipeline_id) {
                 Some(source_pipeline) => source_pipeline,
-                None => return warn!("Script loaded url in closed iframe {}.", load_info.parent_pipeline_id),
+                None => return warn!("Script loaded url in closed iframe {}.", load_info.info.parent_pipeline_id),
             };
 
             // If no url is specified, reload.
@@ -1384,7 +1390,7 @@ impl<Message, LTF, STF> Constellation<Message, LTF, STF>
                 LoadData::new(url, None, None)
             });
 
-            let is_private = load_info.is_private || source_pipeline.is_private;
+            let is_private = load_info.info.is_private || source_pipeline.is_private;
 
             let window_size = old_pipeline.and_then(|old_pipeline| old_pipeline.size);
 
@@ -1396,20 +1402,65 @@ impl<Message, LTF, STF> Constellation<Message, LTF, STF>
         };
 
         // Create the new pipeline, attached to the parent and push to pending frames
-        self.new_pipeline(load_info.new_pipeline_id,
-                          load_info.frame_id,
-                          Some((load_info.parent_pipeline_id, load_info.frame_type)),
+        self.new_pipeline(load_info.info.new_pipeline_id,
+                          load_info.info.frame_id,
+                          Some((load_info.info.parent_pipeline_id, load_info.info.frame_type)),
                           window_size,
                           load_data,
                           load_info.sandbox,
                           is_private);
 
         self.pending_frames.push(FrameChange {
-            frame_id: load_info.frame_id,
+            frame_id: load_info.info.frame_id,
             old_pipeline_id: load_info.old_pipeline_id,
-            new_pipeline_id: load_info.new_pipeline_id,
+            new_pipeline_id: load_info.info.new_pipeline_id,
             document_ready: false,
-            replace: load_info.replace,
+            replace: load_info.info.replace,
+        });
+    }
+
+    fn handle_script_loaded_about_blank_in_iframe_msg(&mut self,
+                                                      load_info: IFrameLoadInfo,
+                                                      layout_sender: IpcSender<LayoutControlMsg>) {
+        let IFrameLoadInfo {
+            parent_pipeline_id,
+            new_pipeline_id,
+            frame_type,
+            replace,
+            frame_id,
+            is_private,
+        } = load_info;
+
+        let pipeline = {
+            let parent_pipeline = match self.pipelines.get(&parent_pipeline_id) {
+                Some(parent_pipeline) => parent_pipeline,
+                None => return warn!("Script loaded url in closed iframe {}.", parent_pipeline_id),
+            };
+
+            let script_sender = parent_pipeline.script_chan.clone();
+
+            let url = ServoUrl::parse("about:blank").expect("infallible");
+            Pipeline::new(new_pipeline_id,
+                          frame_id,
+                          Some((parent_pipeline_id, frame_type)),
+                          script_sender,
+                          layout_sender,
+                          self.compositor_proxy.clone_compositor_proxy(),
+                          is_private || parent_pipeline.is_private,
+                          url,
+                          None,
+                          parent_pipeline.visible)
+        };
+
+        assert!(!self.pipelines.contains_key(&new_pipeline_id));
+        self.pipelines.insert(new_pipeline_id, pipeline);
+
+        self.pending_frames.push(FrameChange {
+            frame_id: frame_id,
+            old_pipeline_id: None,
+            new_pipeline_id: new_pipeline_id,
+            document_ready: false,
+            replace: replace,
         });
     }
 

servo/components/constellation/pipeline.rs

@@ -165,8 +165,7 @@ 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: layout_content_process_shutdown_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,
                 };
 
@@ -254,23 +253,23 @@ impl Pipeline {
                                      state.window_size,
                                      state.prev_visibility.unwrap_or(true));
 
-        pipeline.notify_visibility();
-
         Ok((pipeline, child_process))
     }
 
-    fn new(id: PipelineId,
-           frame_id: FrameId,
-           parent_info: Option<(PipelineId, FrameType)>,
-           script_chan: Rc<ScriptChan>,
-           layout_chan: IpcSender<LayoutControlMsg>,
-           compositor_proxy: Box<CompositorProxy + 'static + Send>,
-           is_private: bool,
-           url: ServoUrl,
-           size: Option<TypedSize2D<f32, PagePx>>,
-           visible: bool)
-           -> Pipeline {
-        Pipeline {
+    /// Creates a new `Pipeline`, after the script and layout threads have been
+    /// spawned.
+    pub fn new(id: PipelineId,
+               frame_id: FrameId,
+               parent_info: Option<(PipelineId, FrameType)>,
+               script_chan: Rc<ScriptChan>,
+               layout_chan: IpcSender<LayoutControlMsg>,
+               compositor_proxy: Box<CompositorProxy + 'static + Send>,
+               is_private: bool,
+               url: ServoUrl,
+               size: Option<TypedSize2D<f32, PagePx>>,
+               visible: bool)
+               -> Pipeline {
+        let pipeline = Pipeline {
             id: id,
             frame_id: frame_id,
             parent_info: parent_info,
@@ -284,7 +283,11 @@ impl Pipeline {
             running_animations: false,
             visible: visible,
             is_private: is_private,
-        }
+        };
+
+        pipeline.notify_visibility();
+
+        pipeline
     }
 
     pub fn exit(&self) {
@@ -424,6 +427,7 @@ 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,
@@ -448,7 +452,7 @@ impl UnprivilegedPipelineContent {
                     self.font_cache_thread,
                     self.time_profiler_chan,
                     self.mem_profiler_chan,
-                    self.layout_content_process_shutdown_chan,
+                    Some(self.layout_content_process_shutdown_chan),
                     self.webrender_api_sender,
                     self.prefs.get("layout.threads").expect("exists").value()
                         .as_u64().expect("count") as usize);

servo/components/layout_thread/lib.rs

@@ -246,7 +246,7 @@ impl LayoutThreadFactory for LayoutThread {
               font_cache_thread: FontCacheThread,
               time_profiler_chan: time::ProfilerChan,
               mem_profiler_chan: mem::ProfilerChan,
-              content_process_shutdown_chan: IpcSender<()>,
+              content_process_shutdown_chan: Option<IpcSender<()>>,
               webrender_api_sender: webrender_traits::RenderApiSender,
               layout_threads: usize) {
         thread::spawn_named(format!("LayoutThread {:?}", id),
@@ -278,7 +278,9 @@ impl LayoutThreadFactory for LayoutThread {
                     layout.start();
                 }, reporter_name, sender, Msg::CollectReports);
             }
-            let _ = content_process_shutdown_chan.send(());
+            if let Some(content_process_shutdown_chan) = content_process_shutdown_chan {
+                let _ = content_process_shutdown_chan.send(());
+            }
         });
     }
 }

servo/components/layout_traits/lib.rs

@@ -44,7 +44,7 @@ pub trait LayoutThreadFactory {
               font_cache_thread: FontCacheThread,
               time_profiler_chan: time::ProfilerChan,
               mem_profiler_chan: mem::ProfilerChan,
-              content_process_shutdown_chan: IpcSender<()>,
+              content_process_shutdown_chan: Option<IpcSender<()>>,
               webrender_api_sender: webrender_traits::RenderApiSender,
               layout_threads: usize);
 }

servo/components/script/dom/htmliframeelement.rs

@@ -20,6 +20,7 @@ use dom::bindings::conversions::ToJSValConvertible;
 use dom::bindings::error::{Error, ErrorResult, Fallible};
 use dom::bindings::inheritance::Castable;
 use dom::bindings::js::{JS, LayoutJS, MutNullableHeap, Root};
+use dom::bindings::refcounted::Trusted;
 use dom::bindings::reflector::Reflectable;
 use dom::bindings::str::DOMString;
 use dom::browsingcontext::BrowsingContext;
@@ -42,14 +43,16 @@ use js::jsval::{NullValue, UndefinedValue};
 use msg::constellation_msg::{FrameType, FrameId, PipelineId, TraversalDirection};
 use net_traits::response::HttpsState;
 use script_layout_interface::message::ReflowQueryType;
-use script_thread::ScriptThread;
-use script_traits::{IFrameLoadInfo, LoadData, MozBrowserEvent, ScriptMsg as ConstellationMsg};
+use script_thread::{ScriptThread, Runnable};
+use script_traits::{IFrameLoadInfo, IFrameLoadInfoWithData, LoadData};
+use script_traits::{MozBrowserEvent, NewLayoutInfo, ScriptMsg as ConstellationMsg};
 use script_traits::IFrameSandboxState::{IFrameSandboxed, IFrameUnsandboxed};
 use servo_atoms::Atom;
 use servo_url::ServoUrl;
 use std::cell::Cell;
 use style::attr::{AttrValue, LengthOrPercentageOrAuto};
 use style::context::ReflowGoal;
+use task_source::TaskSource;
 use util::prefs::PREFS;
 use util::servo_version;
 
@@ -66,6 +69,12 @@ bitflags! {
     }
 }
 
+#[derive(PartialEq)]
+enum ProcessingMode {
+    FirstTime,
+    NotFirstTime,
+}
+
 #[dom_struct]
 pub struct HTMLIFrameElement {
     htmlelement: HTMLElement,
@@ -131,20 +140,46 @@ impl HTMLIFrameElement {
 
         let global_scope = window.upcast::<GlobalScope>();
         let load_info = IFrameLoadInfo {
-            load_data: load_data,
             parent_pipeline_id: global_scope.pipeline_id(),
             frame_id: self.frame_id,
-            old_pipeline_id: old_pipeline_id,
             new_pipeline_id: new_pipeline_id,
-            sandbox: sandboxed,
             is_private: private_iframe,
             frame_type: frame_type,
             replace: replace,
         };
-        global_scope
-              .constellation_chan()
-              .send(ConstellationMsg::ScriptLoadedURLInIFrame(load_info))
-              .unwrap();
+
+        if load_data.as_ref().map_or(false, |d| d.url.as_str() == "about:blank") {
+            let (pipeline_sender, pipeline_receiver) = ipc::channel().unwrap();
+
+            global_scope
+                  .constellation_chan()
+                  .send(ConstellationMsg::ScriptLoadedAboutBlankInIFrame(load_info, pipeline_sender))
+                  .unwrap();
+
+            let new_layout_info = NewLayoutInfo {
+                parent_info: Some((global_scope.pipeline_id(), frame_type)),
+                new_pipeline_id: new_pipeline_id,
+                frame_id: self.frame_id,
+                load_data: load_data.unwrap(),
+                pipeline_port: pipeline_receiver,
+                content_process_shutdown_chan: None,
+                window_size: None,
+                layout_threads: PREFS.get("layout.threads").as_u64().expect("count") as usize,
+            };
+
+            ScriptThread::process_attach_layout(new_layout_info);
+        } else {
+            let load_info = IFrameLoadInfoWithData {
+                info: load_info,
+                load_data: load_data,
+                old_pipeline_id: old_pipeline_id,
+                sandbox: sandboxed,
+            };
+            global_scope
+                  .constellation_chan()
+                  .send(ConstellationMsg::ScriptLoadedURLInIFrame(load_info))
+                  .unwrap();
+        }
 
         if PREFS.is_mozbrowser_enabled() {
             // https://developer.mozilla.org/en-US/docs/Web/Events/mozbrowserloadstart
@@ -152,9 +187,23 @@ impl HTMLIFrameElement {
         }
     }
 
-    pub fn process_the_iframe_attributes(&self) {
+    /// https://html.spec.whatwg.org/multipage/#process-the-iframe-attributes
+    fn process_the_iframe_attributes(&self, mode: ProcessingMode) {
+        // TODO: srcdoc
+
+        // https://github.com/whatwg/html/issues/490
+        if mode == ProcessingMode::FirstTime && !self.upcast::<Element>().has_attribute(&local_name!("src")) {
+            let window = window_from_node(self);
+            let event_loop = window.dom_manipulation_task_source();
+            let _ = event_loop.queue(box IframeLoadEventSteps::new(self),
+                                     window.upcast());
+            return;
+        }
+
         let url = self.get_url();
 
+        // TODO: check ancestor browsing contexts for same URL
+
         let document = document_from_node(self);
         self.navigate_or_reload_child_browsing_context(
             Some(LoadData::new(url, document.get_referrer_policy(), Some(document.url()))), false);
@@ -171,6 +220,16 @@ impl HTMLIFrameElement {
         }
     }
 
+    fn create_nested_browsing_context(&self) {
+        // Synchronously create a new context and navigate it to about:blank.
+        let url = ServoUrl::parse("about:blank").unwrap();
+        let document = document_from_node(self);
+        let load_data = LoadData::new(url,
+                                      document.get_referrer_policy(),
+                                      Some(document.url().clone()));
+        self.navigate_or_reload_child_browsing_context(Some(load_data), false);
+    }
+
     pub fn update_pipeline_id(&self, new_pipeline_id: PipelineId) {
         self.pipeline_id.set(Some(new_pipeline_id));
 
@@ -272,7 +331,11 @@ impl HTMLIFrameElement {
         self.pipeline_id.get()
             .and_then(|pipeline_id| ScriptThread::find_document(pipeline_id))
             .and_then(|document| {
-                if self.global().get_url().origin() == document.global().get_url().origin() {
+                // FIXME(#10964): this should use the Document's origin and the
+                //                origin of the incumbent settings object.
+                let contained_url = document.global().get_url();
+                if self.global().get_url().origin() == contained_url.origin() ||
+                   contained_url.as_str() == "about:blank" {
                     Some(Root::from_ref(document.window()))
                 } else {
                     None
@@ -458,18 +521,7 @@ impl HTMLIFrameElementMethods for HTMLIFrameElement {
 
     // https://html.spec.whatwg.org/multipage/#dom-iframe-contentdocument
     fn GetContentDocument(&self) -> Option<Root<Document>> {
-        self.get_content_window().and_then(|window| {
-            // FIXME(#10964): this should use the Document's origin and the
-            //                origin of the incumbent settings object.
-            let self_url = self.get_url();
-            let win_url = window_from_node(self).get_url();
-
-            if UrlHelper::SameOrigin(&self_url, &win_url) {
-                Some(window.Document())
-            } else {
-                None
-            }
-        })
+        self.get_content_window().map(|window| window.Document())
     }
 
     // Experimental mozbrowser implementation is based on the webidl
@@ -601,19 +653,17 @@ impl VirtualMethods for HTMLIFrameElement {
                 }));
             },
             &local_name!("src") => {
-                if let AttributeMutation::Set(_) = mutation {
-                    // https://html.spec.whatwg.org/multipage/#the-iframe-element
-                    // "Similarly, whenever an iframe element with a non-null nested browsing context
-                    // but with no srcdoc attribute specified has its src attribute set, changed, or removed,
-                    // the user agent must process the iframe attributes,"
-                    // but we can't check that directly, since the child browsing context
-                    // may be in a different script thread. Instread, we check to see if the parent
-                    // is in a document tree and has a browsing context, which is what causes
-                    // the child browsing context to be created.
-                    if self.upcast::<Node>().is_in_doc_with_browsing_context() {
-                        debug!("iframe {} src set while in browsing context.", self.frame_id);
-                        self.process_the_iframe_attributes();
-                    }
+                // https://html.spec.whatwg.org/multipage/#the-iframe-element
+                // "Similarly, whenever an iframe element with a non-null nested browsing context
+                // but with no srcdoc attribute specified has its src attribute set, changed, or removed,
+                // the user agent must process the iframe attributes,"
+                // but we can't check that directly, since the child browsing context
+                // may be in a different script thread. Instread, we check to see if the parent
+                // is in a document tree and has a browsing context, which is what causes
+                // the child browsing context to be created.
+                if self.upcast::<Node>().is_in_doc_with_browsing_context() {
+                    debug!("iframe {} src set while in browsing context.", self.frame_id);
+                    self.process_the_iframe_attributes(ProcessingMode::NotFirstTime);
                 }
             },
             _ => {},
@@ -642,7 +692,8 @@ impl VirtualMethods for HTMLIFrameElement {
         // iframe attributes for the "first time"."
         if self.upcast::<Node>().is_in_doc_with_browsing_context() {
             debug!("iframe {} bound to browsing context.", self.frame_id);
-            self.process_the_iframe_attributes();
+            self.create_nested_browsing_context();
+            self.process_the_iframe_attributes(ProcessingMode::FirstTime);
         }
     }
 
@@ -667,7 +718,7 @@ impl VirtualMethods for HTMLIFrameElement {
                 //                HTMLIFrameElement::contentDocument.
                 let self_url = self.get_url();
                 let win_url = window_from_node(self).get_url();
-                UrlHelper::SameOrigin(&self_url, &win_url)
+                UrlHelper::SameOrigin(&self_url, &win_url) || self_url.as_str() == "about:blank"
             };
             let (sender, receiver) = if same_origin {
                 (None, None)
@@ -690,3 +741,24 @@ impl VirtualMethods for HTMLIFrameElement {
         }
     }
 }
+
+struct IframeLoadEventSteps {
+    frame_element: Trusted<HTMLIFrameElement>,
+    pipeline_id: PipelineId,
+}
+
+impl IframeLoadEventSteps {
+    fn new(frame_element: &HTMLIFrameElement) -> IframeLoadEventSteps {
+        IframeLoadEventSteps {
+            frame_element: Trusted::new(frame_element),
+            pipeline_id: frame_element.pipeline_id().unwrap(),
+        }
+    }
+}
+
+impl Runnable for IframeLoadEventSteps {
+    fn handler(self: Box<IframeLoadEventSteps>) {
+        let this = self.frame_element.root();
+        this.iframe_load_event_steps(self.pipeline_id);
+    }
+}

servo/components/script/script_thread.rs

@@ -71,7 +71,8 @@ use js::rust::Runtime;
 use layout_wrapper::ServoLayoutNode;
 use mem::heap_size_of_self_and_children;
 use msg::constellation_msg::{FrameId, FrameType, PipelineId, PipelineNamespace};
-use net_traits::{CoreResourceMsg, IpcSend, Metadata, ReferrerPolicy, ResourceThreads};
+use net_traits::{CoreResourceMsg, FetchMetadata, FetchResponseListener};
+use net_traits::{IpcSend, Metadata, ReferrerPolicy, ResourceThreads};
 use net_traits::image_cache_thread::{ImageCacheChan, ImageCacheResult, ImageCacheThread};
 use net_traits::request::{CredentialsMode, Destination, RequestInit};
 use net_traits::storage_thread::StorageType;
@@ -82,7 +83,7 @@ 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 +435,9 @@ 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>,
 
@@ -602,6 +606,17 @@ impl ScriptThread {
         });
     }
 
+    pub fn process_attach_layout(new_layout_info: NewLayoutInfo) {
+        SCRIPT_THREAD_ROOT.with(|root| {
+            if let Some(script_thread) = root.get() {
+                let script_thread = unsafe { &*script_thread };
+                script_thread.profile_event(ScriptThreadEventCategory::AttachLayout, || {
+                    script_thread.handle_new_layout(new_layout_info);
+                })
+            }
+        });
+    }
+
     pub fn find_document(id: PipelineId) -> Option<Root<Document>> {
         SCRIPT_THREAD_ROOT.with(|root| root.get().and_then(|script_thread| {
             let script_thread = unsafe { &*script_thread };
@@ -681,6 +696,8 @@ 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 +1196,6 @@ impl ScriptThread {
             load_data,
             window_size,
             pipeline_port,
-            layout_to_constellation_chan,
             content_process_shutdown_chan,
             layout_threads,
         } = new_layout_info;
@@ -1193,7 +1209,7 @@ 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,
@@ -1215,7 +1231,11 @@ impl ScriptThread {
         let new_load = InProgressLoad::new(new_pipeline_id, frame_id, parent_info,
                                            layout_chan, window_size,
                                            load_data.url.clone());
-        self.start_page_load(new_load, load_data);
+        if load_data.url.as_str() == "about:blank" {
+            self.start_page_load_about_blank(new_load);
+        } else {
+            self.start_page_load(new_load, load_data);
+        }
     }
 
     fn handle_loads_complete(&self, pipeline: PipelineId) {
@@ -1641,7 +1661,8 @@ impl ScriptThread {
 
     /// Notify the containing document of a child frame that has completed loading.
     fn handle_frame_load_event(&self, parent_id: PipelineId, frame_id: FrameId, child_id: PipelineId) {
-        match self.documents.borrow().find_iframe(parent_id, frame_id) {
+        let iframe = self.documents.borrow().find_iframe(parent_id, frame_id);
+        match iframe {
             Some(iframe) => iframe.iframe_load_event_steps(child_id),
             None => warn!("Message sent to closed pipeline {}.", parent_id),
         }
@@ -2014,7 +2035,8 @@ impl ScriptThread {
                               replace: bool) {
         match frame_id {
             Some(frame_id) => {
-                if let Some(iframe) = self.documents.borrow().find_iframe(parent_pipeline_id, frame_id) {
+                let iframe = self.documents.borrow().find_iframe(parent_pipeline_id, frame_id);
+                if let Some(iframe) = iframe {
                     iframe.navigate_or_reload_child_browsing_context(Some(load_data), replace);
                 }
             }
@@ -2092,6 +2114,23 @@ impl ScriptThread {
         self.incomplete_loads.borrow_mut().push(incomplete);
     }
 
+    /// Synchronously fetch `about:blank`. Stores the `InProgressLoad`
+    /// argument until a notification is received that the fetch is complete.
+    fn start_page_load_about_blank(&self, incomplete: InProgressLoad) {
+        let id = incomplete.pipeline_id;
+
+        self.incomplete_loads.borrow_mut().push(incomplete);
+
+        let url = ServoUrl::parse("about:blank").unwrap();
+        let mut context = ParserContext::new(id, url.clone());
+
+        let mut meta = Metadata::default(url);
+        meta.set_content_type(Some(&mime!(Text / Html)));
+        context.process_response(Ok(FetchMetadata::Unfiltered(meta)));
+        context.process_response_chunk(vec![]);
+        context.process_response_eof(Ok(()));
+    }
+
     fn handle_parsing_complete(&self, id: PipelineId) {
         let document = match self.documents.borrow().find_document(id) {
             Some(document) => document,

servo/components/script_layout_interface/message.rs

@@ -142,6 +142,6 @@ pub struct NewLayoutThreadInfo {
     pub constellation_chan: IpcSender<ConstellationMsg>,
     pub script_chan: IpcSender<ConstellationControlMsg>,
     pub image_cache_thread: ImageCacheThread,
-    pub content_process_shutdown_chan: IpcSender<()>,
+    pub content_process_shutdown_chan: Option<IpcSender<()>>,
     pub layout_threads: usize,
 }

servo/components/script_traits/lib.rs

@@ -177,10 +177,8 @@ 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: IpcSender<()>,
+    pub content_process_shutdown_chan: Option<IpcSender<()>>,
     /// Number of threads to use for layout.
     pub layout_threads: usize,
 }
@@ -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.
@@ -492,21 +492,15 @@ pub enum IFrameSandboxState {
     IFrameUnsandboxed
 }
 
-/// Specifies the information required to load a URL in an iframe.
+/// Specifies the information required to load an iframe.
 #[derive(Deserialize, Serialize)]
 pub struct IFrameLoadInfo {
-    /// Load data containing the url to load
-    pub load_data: Option<LoadData>,
     /// Pipeline ID of the parent of this iframe
     pub parent_pipeline_id: PipelineId,
     /// The ID for this iframe.
     pub frame_id: FrameId,
-    /// The old pipeline ID for this iframe, if a page was previously loaded.
-    pub old_pipeline_id: Option<PipelineId>,
     /// The new pipeline ID that the iframe has generated.
     pub new_pipeline_id: PipelineId,
-    /// Sandbox type of this iframe
-    pub sandbox: IFrameSandboxState,
     ///  Whether this iframe should be considered private
     pub is_private: bool,
     /// Whether this iframe is a mozbrowser iframe
@@ -516,6 +510,19 @@ pub struct IFrameLoadInfo {
     pub replace: bool,
 }
 
+/// Specifies the information required to load a URL in an iframe.
+#[derive(Deserialize, Serialize)]
+pub struct IFrameLoadInfoWithData {
+    /// The information required to load an iframe.
+    pub info: IFrameLoadInfo,
+    /// Load data containing the url to load
+    pub load_data: Option<LoadData>,
+    /// The old pipeline ID for this iframe, if a page was previously loaded.
+    pub old_pipeline_id: Option<PipelineId>,
+    /// Sandbox type of this iframe
+    pub sandbox: IFrameSandboxState,
+}
+
 // https://developer.mozilla.org/en-US/docs/Web/API/Using_the_Browser_API#Events
 /// The events fired in a Browser API context (`<iframe mozbrowser>`)
 #[derive(Deserialize, Serialize)]

servo/components/script_traits/script_msg.rs

@@ -6,6 +6,8 @@ use AnimationState;
 use CompositorEvent;
 use DocumentState;
 use IFrameLoadInfo;
+use IFrameLoadInfoWithData;
+use LayoutControlMsg;
 use LoadData;
 use MozBrowserEvent;
 use WorkerGlobalScopeInit;
@@ -105,7 +107,9 @@ pub enum ScriptMsg {
     /// Notifies constellation that an iframe's visibility has been changed.
     VisibilityChangeComplete(PipelineId, bool),
     /// A load has been requested in an IFrame.
-    ScriptLoadedURLInIFrame(IFrameLoadInfo),
+    ScriptLoadedURLInIFrame(IFrameLoadInfoWithData),
+    /// A load of `about:blank` has been completed in an IFrame.
+    ScriptLoadedAboutBlankInIFrame(IFrameLoadInfo, IpcSender<LayoutControlMsg>),
     /// Requests that the constellation set the contents of the clipboard
     SetClipboardContents(String),
     /// Mark a new document as active