Forward stop[Immediate]Propagation to original event in CommandRegistry

Previously, stopping propagation would work on the synthetic bubbling
phase of the command registry itself, but the original event would
continue to propagate which is counterintuitive.

spec/command-registry-spec.coffee

@@ -66,8 +66,11 @@ describe "CommandRegistry", ->
       registry.add '.child', 'command', -> calls.push('child-2')
       registry.add '.child', 'command', (event) -> calls.push('child-1'); event.stopPropagation()
 
-      grandchild.dispatchEvent(new CustomEvent('command', bubbles: true))
+      dispatchedEvent = new CustomEvent('command', bubbles: true)
+      spyOn(dispatchedEvent, 'stopPropagation')
+      grandchild.dispatchEvent(dispatchedEvent)
       expect(calls).toEqual ['child-1', 'child-2']
+      expect(dispatchedEvent.stopPropagation).toHaveBeenCalled()
 
     it "stops invoking callbacks when .stopImmediatePropagation() is called on the event", ->
       calls = []
@@ -76,8 +79,21 @@ describe "CommandRegistry", ->
       registry.add '.child', 'command', -> calls.push('child-2')
       registry.add '.child', 'command', (event) -> calls.push('child-1'); event.stopImmediatePropagation()
 
-      grandchild.dispatchEvent(new CustomEvent('command', bubbles: true))
+      dispatchedEvent = new CustomEvent('command', bubbles: true)
+      spyOn(dispatchedEvent, 'stopImmediatePropagation')
+      grandchild.dispatchEvent(dispatchedEvent)
       expect(calls).toEqual ['child-1']
+      expect(dispatchedEvent.stopImmediatePropagation).toHaveBeenCalled()
+
+    it "forwards .preventDefault() calls from the synthetic event to the original", ->
+      calls = []
+
+      registry.add '.child', 'command', (event) -> event.preventDefault()
+
+      dispatchedEvent = new CustomEvent('command', bubbles: true)
+      spyOn(dispatchedEvent, 'preventDefault')
+      grandchild.dispatchEvent(dispatchedEvent)
+      expect(dispatchedEvent.preventDefault).toHaveBeenCalled()
 
     it "allows listeners to be removed via a disposable returned by ::add", ->
       calls = []

src/command-registry.coffee

@@ -179,24 +179,26 @@ class CommandRegistry
     @listenersByCommandName = _.deepClone(snapshot)
     @setRootNode(rootNode) # restore listeners for commands in snapshot
 
-  handleCommandEvent: (event) =>
+  handleCommandEvent: (originalEvent) =>
     propagationStopped = false
     immediatePropagationStopped = false
     matched = false
-    currentTarget = event.target
+    currentTarget = originalEvent.target
 
-    syntheticEvent = Object.create event,
+    syntheticEvent = Object.create originalEvent,
       eventPhase: value: Event.BUBBLING_PHASE
       currentTarget: get: -> currentTarget
       stopPropagation: value: ->
+        originalEvent.stopPropagation()
         propagationStopped = true
       stopImmediatePropagation: value: ->
+        originalEvent.stopImmediatePropagation()
         propagationStopped = true
         immediatePropagationStopped = true
 
     loop
       matchingListeners =
-        (@listenersByCommandName[event.type] ? [])
+        (@listenersByCommandName[originalEvent.type] ? [])
           .filter (listener) -> currentTarget.webkitMatchesSelector(listener.selector)
           .sort (a, b) -> a.compare(b)