[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..eecfaa8f6553a77867654ecf396d3fcbd02bc150 100644
--- a/third_party/WebKit/Source/modules/serviceworkers/ExtendableEvent.cpp
+++ b/third_party/WebKit/Source/modules/serviceworkers/ExtendableEvent.cpp
@@ -52,18 +52,27 @@ ExtendableEvent::~ExtendableEvent() {}
 void ExtendableEvent::waitUntil(ScriptState* script_state,
                                 ScriptPromise script_promise,
                                 ExceptionState& exception_state) {
-  if (observer_)
-    observer_->WaitUntil(script_state, script_promise, exception_state);
+  if (created_by_script_) {
+    exception_state.ThrowDOMException(
+        kInvalidStateError,
+        "Can not call waitUntil on a script constructed ExtendableEvent.");
+    return;
+  }
+
+  DCHECK(observer_);
+  observer_->WaitUntil(script_state, script_promise, exception_state);
 }
 
 ExtendableEvent::ExtendableEvent(const AtomicString& type,
                                  const ExtendableEventInit& initializer)
-    : Event(type, initializer) {}
+    : Event(type, initializer), created_by_script_(true) {}
 
 ExtendableEvent::ExtendableEvent(const AtomicString& type,
                                  const ExtendableEventInit& initializer,
                                  WaitUntilObserver* observer)
-    : Event(type, initializer), observer_(observer) {}
+    : Event(type, initializer),
+      created_by_script_(false),
+      observer_(observer) {}
 
 const AtomicString& ExtendableEvent::InterfaceName() const {
   return EventNames::ExtendableEvent;