workers: basic event loop (#3828)

* establish basic event loop for workers
* make "self.close()" inside worker
* remove "runWorkerMessageLoop() - instead manually call global function 
  in Rust when message arrives. This is done in preparation for structured clone
* refactor "WorkerChannel" and use distinct structs for internal 
  and external channels;  "WorkerChannelsInternal" and "WorkerHandle"
* move "State.worker_channels_internal" to "Worker.internal_channels"
* add "WorkerEvent" enum for child->host communication; 
  currently "Message(Buf)" and  "Error(ErrBox)" variants are supported
* add tests for nested workers
* add tests for worker throwing error on startup

1 files changed, 0 insertions, 2 deletions

diff --git a/cli/tests/subdir/test_worker.js b/cli/tests/subdir/test_worker.js
index f0d9fbed6..70e1d8b73 100644
--- a/cli/tests/subdir/test_worker.js
+++ b/cli/tests/subdir/test_worker.js
@@ -1,6 +1,5 @@
 let thrown = false;
 
-// TODO(bartlomieju): add test for throwing in web worker
 if (self.name !== "jsWorker") {
   throw Error(`Bad worker name: ${self.name}, expected jsWorker`);
 }
@@ -14,7 +13,6 @@ onmessage = function(e) {
   }
 
   postMessage(e.data);
-
   close();
 };