Auto merge of #12910 - creativcoder:swsender, r=jdm

Implement postMessage for ServiceWorkers

<!-- Please describe your changes on the following line: -->

Fixes #12773
r? @jdm

Changes:
* Implements `postMessage` on `ServiceWorker` object.
* Removes unused channels from sw and their scopes.
* Fixes a crash when calling `scope.script_chan()` in sw-scopes event handling.

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix #12773

<!-- Either: -->
- [X] There are tests for these changes at `tests/html/service-worker`

<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->

<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/12910)
<!-- Reviewable:end -->

components/script_traits/script_msg.rs

@@ -136,6 +136,9 @@ pub enum ScriptMsg {
     LogEntry(Option<PipelineId>, Option<String>, LogEntry),
     /// Notifies the constellation that this pipeline has exited.
     PipelineExited(PipelineId),
+    /// Send messages from postMessage calls from serviceworker
+    /// to constellation for storing in service worker manager
+    ForwardDOMMessage(DOMMessage, Url),
     /// Store the data required to activate a service worker for the given scope
     RegisterServiceWorker(ScopeThings, Url),
     /// Requests that the compositor shut down.
@@ -159,6 +162,10 @@ pub struct ScopeThings {
     pub worker_id: WorkerId,
 }
 
+/// Message that gets passed to service worker scope on postMessage
+#[derive(Deserialize, Serialize, Debug, Clone)]
+pub struct DOMMessage(pub Vec<u8>);
+
 /// Channels to allow service worker manager to communicate with constellation and resource thread
 pub struct SWManagerSenders {
     /// sender for communicating with constellation
@@ -174,6 +181,8 @@ pub enum ServiceWorkerMsg {
     RegisterServiceWorker(ScopeThings, Url),
     /// Timeout message sent by active service workers
     Timeout(Url),
+    /// Message sent by constellation to forward to a running service worker
+    ForwardDOMMessage(DOMMessage, Url),
     /// Exit the service worker manager
     Exit,
 }
@@ -182,5 +191,6 @@ pub enum ServiceWorkerMsg {
 #[derive(Deserialize, Serialize)]
 pub enum SWManagerMsg {
     /// Provide the constellation with a means of communicating with the Service Worker Manager
-    OwnSender(IpcSender<ServiceWorkerMsg>),
+    OwnSender(IpcSender<ServiceWorkerMsg>)
+
 }