Only allow action buttons in persistent notifications per spec update

third_party/WebKit/Source/modules/notifications/Notification.cpp

Index: third_party/WebKit/Source/modules/notifications/Notification.cpp
diff --git a/third_party/WebKit/Source/modules/notifications/Notification.cpp b/third_party/WebKit/Source/modules/notifications/Notification.cpp
index e9a6ef8496814f79e63538f984efc90757cbafcb..17d20e60e9d9f4887f6e1f41fe2dc45f70c341ef 100644
--- a/third_party/WebKit/Source/modules/notifications/Notification.cpp
+++ b/third_party/WebKit/Source/modules/notifications/Notification.cpp
@@ -79,6 +79,11 @@ Notification* Notification::create(ExecutionContext* context, const String& titl
         return nullptr;
     }
 
+    if (!options.actions().isEmpty()) {

[Peter Beverloo, 2015/10/21 17:02:52]

It's unfortunate that the place in the algorithm you chose to insert the
`actions` steps in makes it hard or us to support it in order.

Per the spec:
  (1) Check for `silent` & `vibrate`/`sound`, throw if invalid.
  (2) Check for `renotify` & `tag`, throw if invalid.
  (3) Check for `actions` and persistent, throw if invalid.
  ...

Implementation:
  (1) Check for `action` and persistent, throw if invalid.
  (2) Check for `silent` & `vibrate`/`sound`, throw if invalid.
  ...

This is Web-observable behaviour and could cause discrepancies between
implementations, but I'm not sure how much to care. It's certainly not worth
giving createWebNotificationData knowledge of the type of notification.

[johnme, 2015/10/21 18:11:31]

Hmm yeah, and we can't even move this check after createWebNotificationData
because then it would incorrectly occur after the "Set notification’s data to a
structured clone of options’s data. Rethrow any exceptions." step.

I've updated my spec patch to re-order these.

+        exceptionState.throwTypeError("Actions are only supported for persistent notifications shown using ServiceWorkerRegistration.showNotification().");
+        return nullptr;
+    }
+
     String insecureOriginMessage;
     UseCounter::Feature feature = context->isSecureContext(insecureOriginMessage)
         ? UseCounter::NotificationSecureOrigin