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

Implement postMessage for ServiceWorkers

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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.

---
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- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix #12773

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- [X] There are tests for these changes at `tests/html/service-worker`

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components/script_traits/lib.rs

@@ -71,7 +71,7 @@ use util::ipc::OptionalOpaqueIpcSender;
 use webdriver_msg::{LoadStatus, WebDriverScriptCommand};
 
 pub use script_msg::{LayoutMsg, ScriptMsg, EventResult, LogEntry};
-pub use script_msg::{ServiceWorkerMsg, ScopeThings, SWManagerMsg, SWManagerSenders};
+pub use script_msg::{ServiceWorkerMsg, ScopeThings, SWManagerMsg, SWManagerSenders, DOMMessage};
 
 /// 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.
@@ -212,7 +212,7 @@ pub enum ConstellationControlMsg {
     /// Report an error from a CSS parser for the given pipeline
     ReportCSSError(PipelineId, String, usize, usize, String),
     /// Reload the given page.
-    Reload(PipelineId),
+    Reload(PipelineId)
 }
 
 impl fmt::Debug for ConstellationControlMsg {
@@ -241,7 +241,7 @@ impl fmt::Debug for ConstellationControlMsg {
             DispatchFrameLoadEvent { .. } => "DispatchFrameLoadEvent",
             FramedContentChanged(..) => "FramedContentChanged",
             ReportCSSError(..) => "ReportCSSError",
-            Reload(..) => "Reload",
+            Reload(..) => "Reload"
         })
     }
 }