Specs: Somehow I forgot to make CustomEventTarget inherit from EventTarget.

sky/specs/apis.md

 APIS
 ====
 
 The Sky core API
 ----------------
 
 ```javascript
 module 'sky:core' {
 
   // EVENTS
@@ skipping 13 matching lines @@
   }
 
   callback EventListener any (Event event); // return value is assigned to Event.result
 
   interface EventTarget {
     any dispatchEvent(Event event); // O(N) in total number of listeners for this type in the chain // returns Event.result
     void addEventListener(String type, EventListener listener); // O(1)
     void removeEventListener(String type, EventListener listener); // O(N) in event listeners with that type
   }
 
-  interface CustomEventTarget {
+  interface CustomEventTarget : EventTarget {
     constructor (); // O(1)
     attribute EventTarget parentNode; // getter O(1), setter O(N) in height of tree, throws if this would make a loop
 
     // you can inherit from this to make your object into an event target
   }
 
 
 
   // DOM
 
@@ skipping 262 matching lines @@
 magical imports:
   the core mojo fabric JS API   sky:mojo:fabric:core
   the asyncWait/cancelWait mojo fabric JS API (interface to IPC thread)  sky:mojo:fabric:ipc
   the mojom for the shell, proxying through C++ so that the shell pipe isn't exposed  sky:mojo:shell
   the sky API  sky:core
 ```
 
 TODO(ianh): determine if we want to separate the "this" from the
 Document, especially for Modules, so that exposing a module's element
 doesn't expose the module's exports attribute.