Emit 'marker-added/removed' events on DisplayBuffer

src/app/display-buffer.coffee

@@ -33,6 +33,12 @@ class DisplayBuffer
     @tokenizedBuffer.on 'grammar-changed', (grammar) => @trigger 'grammar-changed', grammar
     @tokenizedBuffer.on 'changed', @handleTokenizedBufferChange
     @buffer.on 'markers-updated', @handleMarkersUpdated
+    @buffer.on 'marker-added', (marker) =>
+      @trigger 'marker-added', @getMarker(marker.id)
+    @buffer.on 'marker-removed', (marker) =>
+      marker = @getMarker(marker.id)
+      delete @markers[marker.id]
+      @trigger 'marker-removed', marker
 
   buildLineMap: ->
     @lineMap = new LineMap
@@ -468,7 +474,7 @@ class DisplayBuffer
   #
   # Returns the {DisplayBufferMarker} (if it exists).
   getMarker: (id) ->
-    @markers[id] ? do =>
+    @markers[id] ?= do =>
       if bufferMarker = @buffer.getMarker(id)
         new DisplayBufferMarker({bufferMarker, displayBuffer: this})
 
@@ -548,7 +554,6 @@ class DisplayBuffer
   ###
   # Internal #
   ###
-
   pauseMarkerObservers: ->
     marker.pauseEvents() for marker in @getMarkers()