[ServiceWorker] Allow waitUntil to be called multiple times asynchronously

third_party/WebKit/Source/modules/serviceworkers/ExtendableEvent.cpp

Index: third_party/WebKit/Source/modules/serviceworkers/ExtendableEvent.cpp
diff --git a/third_party/WebKit/Source/modules/serviceworkers/ExtendableEvent.cpp b/third_party/WebKit/Source/modules/serviceworkers/ExtendableEvent.cpp
index b3aa4da5d83590e6461c62480be5fd65ebe31d13..c7faaf94a0e6a33fd99c5eebd5747eeb2cbe4047 100644
--- a/third_party/WebKit/Source/modules/serviceworkers/ExtendableEvent.cpp
+++ b/third_party/WebKit/Source/modules/serviceworkers/ExtendableEvent.cpp
@@ -52,8 +52,19 @@ ExtendableEvent::~ExtendableEvent() {}
 void ExtendableEvent::waitUntil(ScriptState* script_state,
                                 ScriptPromise script_promise,
                                 ExceptionState& exception_state) {
-  if (observer_)
-    observer_->WaitUntil(script_state, script_promise, exception_state);
+  // WPT test:
+  // external/wpt/service-workers/service-worker/
+  // extendable-event-async-waituntil.https.html
+  // 'Test calling waitUntil on a script constructed ExtendableEvent throws
+  // exception'

[falken, 2017/05/25 07:23:23]

Ah sorry I meant to just link in the codereview.

I don't think the spec specifically disallows waitUntil on a script-contructed
event. It just falls into the "If the pending promises count is zero and the
dispatch flag is unset, then" part.

We can just remove this comment.

[leonhsl(Using Gerrit), 2017/05/25 10:11:36]

Oops, got it, removed this comment and updated CL description. Thanks!

+  if (!observer_) {
+    exception_state.ThrowDOMException(
+        kInvalidStateError,
+        "Can not call waitUntil on a script constructed ExtendableEvent.");
+    return;
+  }
+
+  observer_->WaitUntil(script_state, script_promise, exception_state);
 }
 
 ExtendableEvent::ExtendableEvent(const AtomicString& type,